Yes the book does end very abruptly, the point being he doesn't change, doesn't get caught and just continues living his horrible, useless life. And as gross as the movie was, it was incredibly tame compared to the rest of the book. There was some idea of making it worse by leaving more to imagination or something- don't completely remember what the interview I read said. Buuuut I hated the book and thought the movie was ok so I'm probably not the one to talk to about it.
Oh, and there should be lots of summer hanging out!