shantanubala

Read Hesse's Siddhartha if you're thinking along the lines of culture/religion/philosophy.

And read Surely You're Joking, Mr. Feynman! no matter how you think. It's fantastic.

Fooled By Randomness is also good

Read The Black Swan by Nassim Nicholas Taleb

The Little Prince by Antoine de Saint-Exupery if you're feeling especially playful.

I'd recommend it too. It's pretty good

Read We by Yevgheny Zamyatin if you want an interesting allegory

The Giver by Lois Lowry if you want more dystopias.

Read Unweaving the Rainbow by Richard Dawkins if you're very interested in the sciences.

Read a few Ayn Rand books if you like libertarianism and don't really care to relate to the characters.