God Emperor of Dune: Frank Herbert

Book Four in the Magnificent Dune Chronicles-the Bestselling Science Fiction Adventure of All Time
Millennia have passed on Arrakis, and the once-desert planet is green with life. Leto Atreides, the son of the world`s savior, the Emperor Paul Muad`Dib, is still alive but far from human. To preserve humanity`s future, he sacrificed his own by merging with a sandworm, granting him near immortality as God Emperor of Dune for the past thirty-five hundred years.
Leto`s rule is not a benevolent one. His transformation has made not only his appearance but his morality inhuman. A rebellion, led by Siona, a member of the Atreides family, has risen to oppose the despot`s rule. But Siona is unaware that Leto`s vision of a Golden Path for humanity requires her to fulfill a destiny she never wanted-or could possibly conceive....