this reply is just so outdated already, but if you're looking towards an established set of so-called 'best books', you might want to check out the 'Canon' of Literature. There, you'll find the books regarded as masterpieces. Not to be trusted though, as more contemporary listings are already available. The Canon was just especially popular among the Literary crowd during the onset of New Criticism as a way of analysis.
There really is no 'best' book. You, yourself, are the only judge of that. My personal fave thus far, is Lolita.