I'll say why I voted for Maugham. I've read a couple of his books, but the reason he gets my vote is "Of Human Bondage," probably still the best bildungsroman I've read. A massive book that covers the life of its protagonist, Philip Carey, from the age of 10 to about 35 (if I recall) without gaps. It deals deeply with his struggle for meaning and hunt for a belief system. It has a huge number of characters, and they all "live" -- amazing numbers of them are memorable, unique, striking in their behavior and characteristics, yet convincing. It is a book that has much to say and much to teach about people.
Interestingly enough (to me, anyway), I didn't like it when I read it at age 16 or 17 or so. (The thrust was probably too contrary to my beliefs and behaviors). I've never read it again, yet it has evolved to be one of my favorite books because its richness and memories have stayed with me, coming back again and again to mind and illuminating how real the writing and story were. It is a major masterpiece.