God-Emperor of Dune suffers from a bad ending—and this is the third Dune book to have that problem. In Dune Messiah, several hundred pages of complex conspiracy and intrigue resulted in the use of an atomic bomb to do a job that Moe of the Three Stooges could have accomplished with two fingers. (And why bother blinding a prescient in the first place?) In Children of Dune, the rules of the game were changed in the last quarter, when, after more hundreds of pages of equally intricate plotting and counterplotting, the hero suddenly revealed that he had the unsuspected power to become God….

It is a bold step to extend an already massive trilogy by a thousand years. For one thing you must cover a lot of history without lecturing. For another you have lost virtually all of your series characters, and must cajole your readers into...