Reading The God Emperor of Dune for the first time, without knowing that it exists mostly as a long meditation on tyranny and ecology rather than a conventional science fiction adventure, is a specific kind of reading shock. The previous three books were all, at some level, propulsive. God Emperor is not propulsive. It is dense, philosophical, and occasionally dull in the way that very serious things are sometimes dull.

Leto II is Herbert's most sustained thought experiment: a tyrant who hates his own tyranny, who has chosen oppression because the alternative is extinction, who has lived four thousand years and understands things about the species he rules that the species cannot understand about itself. The novel is the record of that understanding in dialogue form.

I think it is Herbert's best book. It is certainly his most ambitious. It is not for people who want more of the original Dune.