A very good work of Science Fiction and the best book I've read so far by Zelazny. It is set on a planet in the future where, the first colonist have taken on the roles of Hindu Gods. The main character takes on the role of the Buddha in order to fight them.
The book moves effortlessly back and forth between describing the action as if it was describing an updated Hindu myth and as if it were describing a typical science fiction novel. This could easily go disastrously wrong, but does not at all. It is filled with incredible imagery and the ambiguity in the description and the metaphysical status of the creatures and events works really well.
I don't know that it has a great deal to say about religion, but it plays with it beautifully, and even Christianity makes an interesting appearance. Rightly deserves its reputation, although it is more a garden of description and play rather than anything deeper.