I recently came across this handout a professor of mine from my undergraduate creative writing program gave us once upon a time. It rings truer than ever.
Great books are, unfortunately, great at different times in your lives; there's a 'window'--in age, experience, sexuality, whatever--when that book might have tremendous impact, or none. A writer needs to look not only at the great questions a book raises, but how the book raises them. So, any master of the craft is a teacher.
Make up your own minds. Prowl around in libraries. If you hear a book mentioned twice in the same month, read it. Stop reading it when you think you should--you, or the author, have made a bad choice. Come back to it later in your life if it haunts you (of if you hear it mentioned twice in the same month).