This is the first book I ever felt the author had became more invested in flipping the bird to her readers than actually creating a sensible story. I'm more amazed that people actually like this story for the content itself. Whoever you are, you're made of a sturdy material than me to withstand all the Nazi science bullshit Roth had thrown at you. Yeah, I said that right. She's more adept at WW2 eugenics than writing actual genetics. 
 I didn't ask so much from an author especially with no background in science to write science except to research about the topic first before you want to create a half-hearted attempt to write around flimsy world-building of yours. I know from the start that the personality faction thing is plain stupid.But using shoddy genetics to write around flimsy Faction logic because it make your story to have some form of sci-fi theme, why bother to put random words "genetic" and "serum" together which doesn't do you any good when you don't even make an attempt to make enough bullshit that its believable enough for someone who actually know genetics or even chemical pathology or who can google. 
 Genetics is just like a general phrase like science. The actual word for it was Molecular Biology because it involve the biology at its molecular level. You even have to study chemistry and pathology topics of it to scratch the itty bit of general knowledge that constitute as genetics (on its own, its the study of hereditary science rather than the actual biology of it). Add to that, you learn the wonderful things with some DNA materials you get from a drop of blood. You learn the structures of nucleic acids, the hydrogen bonds, the codes sequenced in the DNA strands, how it function with all the jumble of DNA enzymes like ligases, polymerases, helicases, how the DNA divide and replicate itself in different cells in mitosis or meiosis and depended on its uses; the protein each codes stand for and how a chain of protein emerge and how DNA send its signals etc. Add to that, you also learn how DNA can sometime have mistakes and when it happen and how it happen and how to fix it or how to suppress it or how to manage it and etc. Other than DNA, you also learn about mRNA, ssDNA, dsRNA, PCR, Electrophoresis, Northern blotting, Southern blotting, Proteomics etc. 
 Above all, you also learn that genetic defects are completely within the natural order of life which not just us humans, but animals and plants and microbials and even organelles that constitute to a form a cellular structure itself. Molecular biology is also what made evolution works and not just a theory and even that was proven as a class of science itself. The study of Genetics also made us aware of diseases and defects which some can take on a lot of features depending on severity and the way to study it and understanding it. 
 You know how it was played in Allegient? 
 "Divergent" means that my genes are healed. Pure. Whole. 
 'Divergent' is the name we decided to give to those who have reached the desired level of genetic healing," 
 Genetically damaged people who have been conditioned by suffering and are not taught to live differently, as the factions would have taught them to, are very destructive. 
 "She's a GP--genetically pure. So she can't understand that--well, it's hard to explain. Just trust me, okay? She's better off staying away for a little while." 
 After all those nice things you can google online, the only thing genetics take precedence in this book was the whole bad experiments going on. And that word again, "genetically damage," the one that's been surfacing throughout the book since the infodump genetic test scene. 
 Its a society of people where everyone was perfect and pure that they dont suffer any other diseases that faulty personality defects basically upend the government to create seeds of authoritarian societies where they're subjugated enough to be even more fascist way of life than the other. They segregate people into factions and build large experimental cities because their genetically modified personality quirks was horrendous enough they have to be isolated and inbred enough just so that they can have "genetically pure and undamaged" lineage. Honey, it doesn't work out that way. Nope. Besides 'pure' lineage isn't always the best genetic lineage, nobody learn about dog breeds? 
 Roth just pasted on the whole idea in this book about factions with 'damaged' genes and Divergents with 'pure' genes as if WW2 never happen where there were thousands of thousands of people killed and those who are experimented on because they're do not fit into the idea of "pure" and assume they have damaged gene. Hence, the Nazi thing. Yes because clearly thats their sick version of scientific genetic logic and to me, this book totally ace that. 
 Genetic mutations can normally occur in any living creature. It can be also expressed in certain population have different hair colour or eye colour or the ability to roll your tongue or to have flexibility than another. Some mutations created species or variances within gene pool. Some is benign and hidden while others is expressed in physical appearance. Microbes evolved being less pathogenic or more pathogenic. Some have genetic defects that was rarer than another which interfere their normal body system and sometimes it affect mental states and sometimes its just a physical features. Point is, calling a person non-Divergent as genetically damaged is like calling a person with hereditary blindness or deafness or even diabetes or cancer as genetically DAMAGED as person. That's not helping at all when you insist on using these labels. Active discrimination on people with genetic defects isn't fictitious. It is real and considering its a Young Adult novel where supposedly the large demographic was the younger audience, you don't think it was not harmful? 
 The Divergent series existed with the idea that we - the free-will and self-thinking people aka the readers - as "Divergent" from Tris's POV. It was also written in the intention to make you as a reader to feel like you're more 'special' than the non-Divergent side characters. Naturally, it made sense why the narrating characters are Divergent themselves (or at least one of them) in the series. But in a way, Roth was discriminating her readers with the way she's writing as if she can escape writing shoddy derogatory things by creative licenses. Oh hail, another version of Jay Kristoff where you could appropriate everything even a foreign culture. 
 It was written in the future, 'of course', she can write like that. But honestly, I never seen anyone who was ignorant to come up a bullshit worldbuilding that called a person "genetically damaged" just because they have "wrong sequence of genes". The quarter of the book was on discussing about how damaged someone was because they're not Divergent. She even didn't write the issue good enough that made it less offensive either. No, in Allegiant, being GD is bad enough that its a bad word that leads to a form of depression because the character isn't human enough. Really? 
 I get that all of these are necessary for angst and more "oh, I'm not special as her and my life suck" drama and the subsequent convincing of "you're perfect just the way you are" conversations and also the part where "everything is going to end badly if we didn't stop it" plot that was inserted out of nowhere. Why does she kept reinforcing her flailing world-building with even more plot holes? 
 If that wasn't bad, I listen to the audiobook version of this book just to feel the differences between the narratives and there was no improvement at all other than levels of sycophancy and occasional weird creepy sentences that made me reevaluate the necessity to listen to this on audiobooks. 
 I've read the last section with author's notes and there's a lot of people involved in this book and nobody think it was bad that she's being discriminatory to everyone or how things get predictable or whether something could work out right between characters to even the flow of the story? 
 I know that there's that issue with the ill-fated ending which I'm sure everyone was spoiled to the brim about. But no, my gruff with this book was mostly about the story structure. In fact, what most of the dual POVs in this book did was focusing too much on drama aspect (I like you, I hate her, I hate him, I want to be you etc) and the infinitesimal amount of two-to-three-syllable characters in this book rather than providing a form of clarity toward the story. I expected it as such since my issues with Insurgent and the whole stream-of-consciousness that was going on in this book. I tolerate the style but for someone who (sort-of) dislike it when it was written badly and pointless, I never understand how on earth someone could stomach all these unfiltered paranoia, feelings angst etc in YA Dystopia. Stylistic literary preference? Does it help strengthen its flaws? Was there even any thought given in this book without everything in shambles? 
 Another thing I don't understand about is the constant repetitions to reassert the idea of factions - again and again. The political situation had changed from the rigid faction to factionless society. There's a lot of repetitive bits of how a person of *insert faction* should think, wear, behave, customs which was completely redundant in the third book. The author can totally skip writing about her character's characterizations, descriptions and plot but she couldn't stop herself from writing and expressing in her narrative character's from inner prejudices and emo thoughts and lust-filled thoughts and shallow thoughts on others. 
 Plus, what was the point of writing a damn huge loads of character if you just spit names and expect people to memorize that and get into the drama? There's always somebody coming around to the narrating character. Talk about something and leave and rinse and repeat for several hundred times to get to this length. I don't know who is who by third chapter alone. There's a thing called character dumping, Yes, that pretty much sum the whole situation up. Too many characters, too little deaths. 
 Besides, all those talk about consistency and clarity, I can't even make sense the plot with the summary of the book in its wikipedia article. 
 Another thing, what was up with these "memory serum virus"? I swear, the author made random deus ex machina out of the whim just to make the situation slightly more intense for the characters. Seriously, since when was a virus have that big memory to cause amnesia? Should it even be called a virus? Why not use nanotechnology or self-induced amnesia or some noisy screwdriver. In fact, serum spore dispersion made more sense than spray-able amnesia viruses. What a waste of technology. 
 Oh, there's also this scene, 
 "The fluid is packed with microcomputers. They are designed to detect specific genetic markers and transmit the data to a computer. It will take them about an hour to give me as much information as I need, though it would take them much longer to read all your genetic material, obviously." 
 Mathew injected these into a person and it can check the "genetic materials" from the inside of the body. I did say in the paragraph way above this that you can get strands of DNAs from a drop of blood. A vial of blood is perfect for a lot of genetic testings but injecting someone with microcomputers into your vein just to detect something a drop of blood will do was plain waste of time, energy and resource. And it took an hour to completely encode your whole genome to readable form. DNA are heat sensitive and thats why its time consuming to isolate, put enzymes and wait for it to work and purify it etc. There's also a need to check for a control just in case it read something other than DNA. Plus, if data interpretation of a DNA was that easy that a person could glance through it and announce they know everything. Most of the time I guarantee you that they're all bullshitting you. It took me a couple of hours of triplicates and weeks of sleepless nights for me to even read data, analyse it, check it with other sources and test it with SPSS to make it read alright for average people to understand and all everyone read in the end was the p-value. At least, realistically, the reaction of the said tester wouldn't be a series of info-dumps. Oh, its science fiction and its a post-CSI verse, I can let that slide and wish as if it was all that easy. 
 Technically, by that GP and GD logic, I am GD as well considering my family history and all. I'm sure I have bad genes somewhere. So am I damaged, Roth? Because the way you write it, it sound very convincing that you have your own prejudices with the idea of genetic purity that worried me. Because nobody in right their mind, would consider using limited vocabularies on a topic that have a lot of variant to choose from considering its a field of study and have its long history and all. At least, know the differences between Eugenics (practice of improving genetic quality) and Genetics (study of heredity). 
 I was slightly looking forward to some improvement since "Insurgent" was plain disappointing and considering the massive fanbase it had, I expected that the editor are be paid more before publishing this but Allegiant is still just as bad as Insurgent. With messy prose and dialogues (it was more apparent if you read out loud and there was so many contradictions in a same sentence and weird descriptive imagery and choice of words on sentences and I'm not even a native English user to notice that there's something really wrong with this phrase "I think you are the only person sharp enough to sharp someone like me". Does it make sense to you because I don't get it.), there's also all these terrible stick characterizations from Tris and Four, then the influx of unnecessary characters and the illegible series of nonsense masqueraded as plot. I hardly see anything that reminded me of the first book. "Divergent" which by itself, isn't that bad but its sequels was the definition of monstrosity. 
 And honestly, all the things that made reading the book a chore made me feel fine with the ending. Since I expected it from all the spoilers everyone gave, but I never expected to feel the ending completely justified. I don't care for the character enough that I was all rooting for it. 
 But was the ending well-done? Of course not, it was plain tasteless. Frankly, its all for the shock value which probably to seed resentment among the existing fanbase. Was it unpredictable? Yeah. The denouement lost its steam. I couldn't wait for it to end. 
 Overall, I guess, the book does serve its purpose. Was it fulfilling, meaningful or deep? Nope, nah, no. Dead negatives. I did say Roth was giving her readers the finger because that exactly what I felt from her book.