HUMOR in science fiction is about as common as originality, which in turn is no more plentiful than giant Godzilla lizards along the New Jersey Turnpike. There were probably more belly laughs at Andropov's funeral than in the latest megaton of space movie tie- ins and post-holocaust yawns. It comes as some relief to welcome the arrival of one barrel of genuine laughs, in Rudy Rucker's new novel, Master of Space and Time.

issues (though the earth does get shaken a bit at one point by a giant Godzilla lizard stalking the New Jersey Turnpike) and seeks answers to no questions larger than the nature and purpose of the universe.

The story is, in a way, a retelling of the old three- wishes fable, the Peasant and the Sausage: Wish #1 is wasted foolishly, Wish #2 goes wrong, and Wish #3 must be used to put things right again. The fable has been retold before (for instance in "The Monkey's Paw"). What makes it new here is that each wish is really a chance at absolute mastery of space and time (including hyperspace and sideways time and every other imaginable variant), that the wisher is well aware of the history of three-wishes fables, and that the author knows how to have fun with all of this.

Rucker's sense of fun is rare indeed. He has been compared to Lewis Carroll, and the comparison is not presumptuous. Like Carroll, Rucker is a mathematician who not only enjoys paradoxes, but can propagate that enjoyment as pure lunatic humor. Why shouldn't the problem of world hunger be solved with porkchop trees and fritter bushes? Why not an alternate universe ruled by Fundamentalists? Why not find a reasonable explanation for Godzilla? Why shouldn't "gluons" (the entities presumed to hold quarks together, and which come in three colors, the rare red, the rarer blue, and the incredibly rare yellow) be able to grant us three wishes?

The humor is not always even. At times Rucker almost slips into mere Douglas Adams whimsy, mostly in chapter titles ("This Is the Name of This Chapter" is the name of one chapter; another is called "100,000,000,000,000,000,000,000,000,000,000, 000"). At other times he soars to the satiric heights of Frederik Pohl. For example, at one point two ugly college kids sitting in a McDonalds come face to face with the Master of Space and Time, who can grant any wish they want -- no more world famine, $10 million dollars, anything. The boy says:

"Think I'd like some marijuana ice cream."

"Yeah, yeah, yeah," said his date, tittering and rocking back and forth in her seat. "With cocaine whipped cream."

"And an LSD cherry," whispered the boy.

The wonderful dumb perversity of human nature is the key subparticle of all the best humor, and it is the stuff which glues together Rudy Rucker's three-ring circus of a world.

PURE FRIVOLITY aside, Rudy Rucker is genuinely curious about space and time, and he shares his curiosity in The Fourth Dimension. Those who think the fourth dimension is nothing but time, and those who never think of it at all, should be encouraged to read this, along with anyone else who feels like opening the hinges of his mind and letting in a bit of fresh air.

Rucker begins with the familiar analogies, showing how Flatland's two-dimensional residents, including "A. Square," would perceive a third dimension. This is the usual approach to 4D. As Flatlanders imagine a cube, so we can imagine a hypercube. However, Rucker departs from the usual approach. He quotes not only from E.A. Abbott's Flatland (whose centennial this book celebrates) but from other flatlands, including Thinland, the Planiverse, even the cave shadowland of Plato's Republic. Rucker keeps dreaming away at Flatland variations of his own: How a human falls through Flatland; 2D life on a spherical surface; how two parallel (plane) worlds get connected through a space door (and how a Flatlander woman can use this to deceive her hexagonal husband).

The most astonishing Flatland dream allows A. Square to come to grips with the fact that he is being dreamed! He even speaks with the Dreamer, who says goodbye. Goodbye? A. Square replies:

"But surely you will always be with me? Is not my World a fragment of your Mind?"

Dreamer: "It's not my mind, really. I'm just filling in. Who knows who'll dream you next. You're the real immortal, Square, not me."

Self-reference and infinite regress provide entertainment along the way as we are introduced to metageometry in the most painless possible way. Rucker discusses everything from time paradoxes to the possibility that the I Ching gives good advice. He explores the interesting fact that spiritualism and the fourth dimension both enjoyed vogues during the late 19th century, and moves on to considerations of the nature of reality. How real is the fourth dimension? When do mathematical dreams (such as the notion that matter is a kind of bump in infinite-dimensional Hilbert space) become reality?

Throughout, the book is as witty as Rucker's fiction. It is further leavened with silly drawings and intriguing little puzzles. The final impression is that Rudy Rucker, if not master of space and time, has certainly become master of a playful, intellectual humor. And that is something as rare as yellow gluons.