I think the best advice I could give for someone in high school is to not take AP English. The normal senior English class is a breeze--don't stress yourself out for no reason. What's more, the class which AP replaces in your freshman year of college is also absolutely nothing. Don't waste your time or effort.
A few people I know read Siddhartha when they were in high school--I know Jon in particular was really impressed by it--but I just kept on reading whatever I felt like because I sure as hell didn't need to actually read any of Ellen Foster to convince my pace-setter English teacher that I was keeping up. And now that I'm actually interested in reading it, I enjoyed Siddhartha quite a bit. Just like Slaughterhouse Five, I feel like my appreciation of it is entirely my own, uninfluenced by some class that's more trouble than its worth. What's more, there is actually quite a few recurrent threads of thought between Slaughterhouse Five and Siddhartha--thinking about it, its a pretty odd coincidence that I happened to read them back to back. In particular the notion of time, and how people fit into it, is very similar between the two. Tralfamadorian time is not unlike the notion of time which Siddhartha envisages while sitting before the river which comes to mean everything to him.
To be honest, I really didn't know much about the book before reading it and assumed that it was a gentle bit of historical fiction--exploring how Siddhartha became the Buddha--but was surprised and quite pleased to see the direction Hesse took it, which is a decidedly existential take on many Buddhist and Hindu beliefs. The message he seems to be striving most of all to get across is that life must be lived including mistakes, one can never really learn wisdom from teachings and even if one agrees with the teachings they must experience it themselves, not take it as given. So now I feel even more justified in dodging homework and coming upon this outside of class. What's interesting, as well, is seeing where some very German concepts push up and coalesce into the Buddhist and Hindu philosophies. Schopenhauer wrote extensively about the Veil of Maya, which is present here both as realism for the Indian characters, as well as seeming to be a critique of Schopenhauer's dogmatic insistence on pessimism. Siddhartha's interest in the river as a sort of "flow of time" call to mind both Anaximander and Nietzsche's later interpretations of him--in particular the idea of existence as constant flux, and that one can never step into the same river twice. And in some of the final passages there is a completely clear Heideggerian notion of man: thrown, and projected into his own future--Siddhartha comments that within the young there is already their approaching death, and within the sinner there is already the repentant, etc.
But what is perhaps the most striking is how Hesse manages to keep these ideas from becoming heady or cumbersome, keeping them within the reach of Siddhartha's own unassuming reach. The prose is spare in a way that leads to many pleasant surprises when a poetic phrase seems to emerge almost out of necessity from the events, as opposed to craftsmanship. And despite its slim size, it seems to take quite some time to get through--each section feels filling, though it is often only a few pages.
I don't know that I would count this as one of the best this year, but I certainly enjoyed it, and can see myself coming back to it almost definitely in the future. Also, its nice to get a bit of a picture for Hesse, who I haven't read at all until now.