East of Eden, hands down. That said, it’s hard to explain why (a short description of this book will always sound dull and boring)—I suppose it’s the character development. It’s truly something else.
Anna Karenina, but not because of Anna (she’s kind of a dickhead); because of Levin. So good.
East of Eden definitely has a place in my top 5. Having been forced to read grapes of wrath in highschool, I didn't touch another Steinbeck for quite a few years. I think being told to read something immediately changes your opinion about the book and author.
East of Eden was a perfect book about humans. Definitely changed the way I think and feel about Steinbeck. Worth every page.