Small Gods by Terry Pratchett According to the premise of this book, gods need believers to exist. The god Om, the national god of Omnia, the most oppressive theocracy in Discworld, is not actually believed in by most of his followers. They believe only in their established church. So when Om accidentally transforms himself into a turtle, most people can't hear his cries. It is only three years after his accidental transformation into a turtle that he runs into one of his true Believers- a novice named Brutha, who is not very clever, but is nonetheless very smart, and has a nearly perfect memory. The evil Vorbis, head exquisitioner, is planning to rule Ephebe, and when he finds out about Brutha's memory, he decides to bring Brutha with. In Ephebe, there are many philosophers. The one with no real followers in Ephebe is a blind philosopher who happens to have written a pamphlet about how the world is on the back of four elephants on the back of a turtle, which is discworld is true. He has, unbeknownst to himself, become a symbol among those wishing to overthrow Vorbis and Omnian rule. Anyhow, throw it all together and you get a rather funny but nonetheless profound story.
Happy reading.