There are some of us who feel that Frank Herbert should never have written a sequel to "Dune," much less three of them. "Dune," given Mr. Herbert's talents and limitations, was just about a perfect science fiction, as well as a lecture on ecology. The desert planet, the giant sand worms, the blue-eyed Fremen, the water suits, the narcotic spice, the God-making, the witches, the telepathy and the prescience—how could they have been improved upon? And they haven't been, not in "Dune Messiah," in "Children of Dune" or in "God Emperor of Dune."

Some of us, however, are outnumbered by hundreds of thousands of readers who insist on a "Dune" redux every five years or so…. Mr. Herbert is the prisoner of a cult, his own Leto. I suspect he would prefer to branch out and risk something else, as he did in "The Green Brain," "Whipping Star," "The Dosadi Experiment" and other novels that have not been nearly so successful as the "Dune" retreads. His cult won't let him….

To read "God Emperor of Dune" without having read its great-grandfather is like meeting Anastasia when you are totally ignorant of Russian history; the glamour is missing. Mr. Herbert depends on ideas for his imaginative effects; his prose has seldom roused itself to sing, and his characters tend to stand around like mailboxes full of mysterious profundities in sealed envelopes, waiting for the weather to change for the worst….

Without giving too much plot away—which would be difficult, because Mr. Herbert is so prodigal with plot that he would embarrass a Robert Ludlum—I will say only that Leto 2d is turning himself into a sand worm. Upon his metamorphosis, the desert will return to Dune.

I admit my addiction [to the "Dune" mythology], even while wishing that Mr. Herbert didn't try so hard to be a poet and a philosopher. He does go on about what Marx called the Asiatic mode of production, and he can't resist sounding like a Brutus with a tin ear, and his whole notion of leadership and uniforms and the elite female palace guard of "Fish Speakers" smacks of an unintentional and undigested fascism, anarchy for the fun of it. Blue eyes will ride sand worms across the desert into freedom.

When you can visit the past, guess the future, read minds and live for 3,000 years, it is easy to suffer. The rest of us are bookworms.