What can I say about Half-Blood? Well, first I'd say it's an obvious Vampire Academy clone. Glaringly obvious, like getting conked on the head with a two by four. A lot of things I liked about this book unfortunately can be attributed to the fact that Vampire Academy is one of my favourite YA series, so I'm not sure if I would have liked it on its own or not? *shrugs* 
 Many, many people have already pointed out the painfully obvious characters/scenes/etc ripped straight out of Vampire Academy, so I won't spend too much time on it. The characters are obvious, although Adrian seems to be split into two characters, Seth and Deacon. Seth has Adrian's wit and is the 'third point of the love triangle', while Deacon has Adrian's vices and laid back attitude. Alex's mother's name is Rachelle (and the author of Vampire Academy is Richelle, SO CLEVER). Hell, Alex even mentions an instructor she had that was attacked by daimons and 'tagged' with scars all over, marring the woman's beauty, just like Natasha Ozera got attacked by Strigoi and scarred in VA. 
 The biggest difference between the two series is the Apollyon, a half-blood that can use magic and obliterate daimons. And if the extremely obvious foreshadowing in the beginning didn't grab you, later they flat out say that Alex is the second Apollyon, since Seth is the first. I suppose it's a good idea in theory, but the Apollyon seems to be the council's bitch just as much as any other half-blood. 
 So, why exactly couldn't better names have been created for the species other than 'pure-blood' and 'half-blood'? It is mentioned that the Hematoi are the Pure-bloods, but no one calls them that, it's always "Pure this" and "Half that". It just grated on me. Unlike in VA, half-bloods don't need pures in any way and vice versa, it seems to me like pures brainwashed halfs into thinking they were needed so they could have slaves or second class citizens. Both pures and halfs fight daimons (where in VA only dhampirs fought Strigoi and protected the Moroi) and halfs can procreate with other species, not just pures. So why aren't the halfs defecting in droves and living out in the real world among normal people? Yes, the pures threaten to turn halfs into mindless slaves with some elixir that takes away their free will, but is the choice always Sentinel or servitude? I don't recall if it was mentioned and we only ever see half-blooded Covenant students. 
 Alex is... no, no thank you. She's supposed to be this tough, snarky, badass chick and for me she just falls flat and comes off more as self-entitled and whiny. Basically, Rose 2.0 she ain't. Aiden isn't that much better. He's very flat and boring, even more so than Dimitri was for me. (And seriously, how does this guy's eyes change to so many different colours? He should go see a doctor.) When it comes to the love story, Alex does have a precedent and says she used to crush on Aiden before she left, but Aiden's attraction to her seems to come right out of the blue. It's a case of good old-fashioned insta-love, something many, many young adult books have. At least I liked Rose in VA despite all her flaws, even without liking Dimitri. Both Alex and Aiden are bleh, just like the majority of the characters in Half-Blood. Seth has potential from what little I saw of him, but other than that? Everyone was just there, feeding or hindering the plot and Alex and Aiden's forbidden love. No thanks. 
 The plot is very basic. Alex's mom dies, she gets dragged back to the Covenant, has to train with Aiden and prove she can be re-admitted, high school crap happens, love story tripe happens, Alex finds out her mom is a daimon, Alex finds out she's the second Apollyon, she leaves the safety of Covenant, gets kidnapped, kills her mom, and finally, is rejected by Aiden because he doesn't want her to be forced into slavery servitude. Too many times I was just reminded of Vampire Academy, except Rose was also ruining Lissa's love life. 
 So one default star for the name Alexandria (a name I love and use in my own fiction) and one shiny star for everything I liked that was torn from Vampire Academy. Cheers.