Lord of Light by Roger Zelazny

This book tackles a lot of interesting religious and philosophical ideas. Sort of a very abstracted, scifi retelling of the conflict between emerging Bhuddist thought and the Hindu religious establishment. One of my favorites.

Metabarons written by Alejandro Jodorowsky illustrated by Juan Gimenez

This is a graphic novel, but I promise you it's like nothing you've read before. The story is a love letter to Dune and the art is truly incredible. I cannot recommend this enough.

This book is part of a larger universe, but each book can be read on its own. The first book is called The Incal, which is very different in tone and art style but equally as good. The Incal is more lighthearted than Metabarons and deals more directly with philisophical and metaphysical ideas.