It's hard to know where to start so I'll just start here: there's insight, there's realism, there's absurdity, there's death, there's intellect, there's stupidity, there's pain, there's every possible kind of humour, there's... everything really; and in that way, I guess the best way to describe it is: comprehensive. 
 Filled with digressions and tangents, entire pages of solid text, run-on sentences, endnotes, end notes with endnotes, a non-linear storyline, well over 1000 pages long, with moments of absurdity nestled inside a stoic realism. Naturally, these elements are not going to appeal to every reader and the technical jargon, acronyms, and essentially singular narrative voice are definitely not going to help. But these features, at least for me, all seemed to add something to the story. Whatever irritation they might bring all seemed worth it when seen as in service to something greater, whether it be to convey realism, to set up a joke, or to articulate one of the themes. 
 Infinite Jest generally deals with darker themes and so will naturally appeal those with darker tastes. Think of Hubert Selby's Last Exit to Brooklyn and Requiem for a Dream mixed with Joseph Heller's Catch-22 and you'll probably get an idea of the book's tone. 
 Like all literary/ character driven stories, you really do need a 'hook' to pull you into the story. For me, that hook was the book's humour. But it also helps to resonate in some way with the characters themselves or the central themes if you need help to (at least initially) look past the author's/ narrator's strange idiosyncrasies (the repeated use of the phrase "and then but...", the endnotes, etc.). But like most idiosyncrasies, you get used to them and over the course of the book, especially one this long, you begin to enjoy them and see them as part of the book's character. 
 I actually came to really enjoy the endnotes. Whether the endnote was a single "sic" or a ten page long filmography, the endnotes always felt like they added an extra dimension to the book, some kind of meta-analytical joke that also served to inform the reader. The dry definitions/ explanations of the various drugs mentioned and used helped the narrator maintain a certain authoritative/ omniscient voice but were always balanced with humorous anecdotal additions that made sure I never got tired or bored with repeatedly flicking back and forth. Sure, a lot of the endnotes could've been inserted into the body of the story without much fuss, but their inclusion seems to add a certain dimension to the narrator as his/ her/ it's own individual character, a sort of neurotic and fastidious academic, someone who seems to exist both within and outside of the story. 
 Throughout the story, there was a constant blurring of the lines between the narrator's and characters' voices. The exact nature of the narrator is still unclear to me. I'm not even sure if there is just one narrator or many communicating to one another throughout the story (given that the narrator describes itself on page 965 as "we" and "a couple of us" among other examples referring to the size of Don Gately's head on page 476). 
 That blurring of narrator and character extends well beyond the use of endnotes. While most of the book is ostensibly written from various third person limited perspectives, the narrative voice remains reasonably consistent as we switch between these perspectives. This means the style and tone and narrative mannerisms remain relatively consistent even as the story switches from the perspective of, say, a clinically depressed and suicidal woman to a young tennis prodigy. I really didn't mind this sameness in voice, especially when the narrator's voice is so engaging. I found having that singular tone helps to thread the characters and the story together, giving the reader the sense the characters are all connected in some fundamental way that isn't necessarily related to the plot. The troubles of one person feel like they can be mapped onto other characters. To learn about one character is to learn about the others and that map (generally a map of suffering) helps to navigate the other individuals. Infinite Jest is more than the analysis of one person or a group of people, it is much broader and inclusive in scope. This feels more like the analysis of an entire culture through disparate yet connected individuals. 
 In an interview with Wallace, Michael Silverblatt described the book as a pane of glass that's been dropped and smashed. That seems like a great analogy to me. The window pane is still there, but it's been fractured into lots of little pieces. Each chapter/ section is like one of those bits of glass that, although it is only a piece, still remains part of something bigger, something more complete and whole. Each chapter and chapter section could be its own short story. 
 The story feels as though it's been deconstructed at some point and carefully, but very deliberately stitched back together. Characters' stories all interact in some way, with characters crossing paths at various points. These interactions aren't overstated, nor do they feel forced or contrived but rather help add to the interconnectedness of the story. 
 Upon reading, I was almost immediately reminded of Joseph Heller's Catch-22. Not only in terms of the satirical humour and its juxtaposition with the rawness of life (where Heller deals with the psychological effects of war, Wallace focuses on poverty and drug addiction) but also in terms of there being multiple layers that, even if you don't recognise or deliberately interpret and contemplate, can nevertheless feel in virtually every word on the page. Knowing, or at least feeling, that the author has put a lot of care into every word makes it that much easier to loose yourself in. It's hard to describe that feeling, but I guess it's a kind of comfort, like you know you're in good hands. And with that feeling, every word becomes more believable, and so the characters and the world make a stronger case for the reality they're trying to convince you of. 
 Really, you could read this book as a post-modern manifesto and try to dissect it 'til the world falls down or you could take it less seriously and simply read it purely for the humour, the drama and the more tangible insights Wallace offers into addiction, depression, and family dynamics. Either approach is just as legitimate as the other. I read it somewhere between these two modes (which says more about my own preferences than anything else) and enjoyed it from start to finish. That being said, upon reading the final page, the plot was very much still up in the air for me. I immediately went back and re-read some sections which added some insight but I ultimately had to resort to internet discussions to really piece the plot together. 
 You don't have to work to enjoy the book but you do have to work if you want to make the most of the many layers this book possesses. The writing itself isn't particularly difficult to read if you don't mind the run-on sentences and digressions and endnotes. The difficulty of Infinite Jest comes, largely, from trying to tease out and contextualise the disparate plot details and some of the more subtle themes and ideas that Wallace was trying to convey (which are spread out over the entirety of the 1100 pages). He raises all kinds of questions around narration, story structures, and the nature of entertainment which I think would require more than one read through to properly appreciate. 
 While I was fully expecting subtler allusions and themes before I even started and looked for them throughout I assumed the plot would more or less work itself out and become obvious to me by the end. I should have known better and am a little annoyed with myself for not paying closer attention to the lines and plot points that stood out to me at the time I read them, but that I didn't slow down enough to examine and contextualise and try to piece together. This is where the humour, I think, stole the show. I wanted to keep reading more for the entertainment than for the actual deeper messages Wallace was trying to convey. Which, for those who have read the book will understand, was a pretty big theme in and of itself and it seems pretty obvious I fell right into the trap. It's a little embarrassing to admit, to be honest. Though I'm sure I'm not alone in this. Wallace said that "if the story didn't make sense then the book has failed for you" which is a little melodramatic. Afterall, one can always re-read and discuss and learn after the fact. 
 The book, I think, is a study in realism. And to that end Wallace was very successful. As in real life, the threads of understanding don't always tie themselves up in a neat bow for us to easily piece together and digest. Wallace was aiming to depict life as honestly as he could and so anything conventional in terms of wrapping up the plot would feel like a violation of that purpose. The story's conclusion, as Wallace has said in interviews, occurs "off the page". Personally, I thought the ending was exactly what it needed to be and feels appropriate given the book's content and themes but you shouldn't go into this expecting a conventional wrap up of all the events, plots, and subplots. Wallace provides the details and leaves it up to the reader to infer what finally happens. So if you haven't read the novel yet but you really want to make the most of it on your first read, I suggest you take your time with it, make notes if you have to, and really follow your gut when it comes to those little (and large) details that are buried in all those pages. 
 There's a lot to love in Infinite Jest. It's a book that feels like it continues to exist beyond the last page, as if it's still being written somewhere, and could probably go on forever. The fragments, the pieces of reality that comprise this book can be seen in everyday life in just as fragmented a way. Like all good fiction, it mirrors life and, in turn, life mirrors it.