I would like to second (third?) Catcher, with the same reasons. I also hated it because Holden tended to gloss over things that may be seen as rather important. Did you know that he was sexually molested by other guys before? Neither did I. It's brought up all of once, VERY VAGUELY, and then completely pushed aside for something else. Characters are introduced with little closure for them and the story, as a whole, is tragically quaint; it's that stupid teenage angst thing that's been done over and over again. It's like "oh, ANOTHER one of these? [sarcasm]I wonder how this one will turn out.[/sarcasm]" Maybe it's because I don't get it, like people tell the OP, but if people don't get your book when they read it, you have done something wrong.
Also, The Book of Negroes is one of the worst books that I have ever read. The characters are ridiculously unrelatable. The worst part is that it's hilariously dated; perhaps I could relate if I lived in slave-era America, but I am living in contemporary Canada and little to none of the things that happen in the book happen here. And it's a recent novel. How a recent novel could be dated, I would not have known if not for this book. It was an ordeal to read for English class, even more than Catcher.