Harry Potter 6 is available as an audiobook on Itunes, but was fifty bucks. For a book I had read, that just seemed like too much, so I went with Jess' suggestion The Graveyard Book and the lastest non-fiction science book by longtime CC girl crush Natalie Angier.
Tom Robbins is awesomesauce and I went through a phase in college where I read everything he had written. "Jitterbug perfume" was my favorite.
I don't know much Terry Pratchett, but "Good Omens" was pretty good.