Island by Aldous Huxley. Easily the best thing he ever wrote.

Steppenwolf by Hermann Hesse. You could probably read it in the original German; I had to read it in translation.

Zen and the Art of Motorcycle Maintenance and Lila both by Robert M. Pirsig. Hard to describe these, so have a look at the dust jackets.

The Universe is Calling by Eric Butterworth. A different twist on prayer.

Grace and Grit by Ken and Treya Wilber. The story of her battle with cancer is used as a vehicle for some excellent philosophical insights.

I hope this helps. I read a lot, and have lots more to recommend. Let me know what you think, and/or post in my diary.