WILL THE the sins of the original be visited upon the sequel? Happily, in the case of Philip Jose' Farmer's Dayworld Rebel (Ace/Putnam, $17.95) this is not the case.

Dayworld set readers down on an Earth more than 2,000 years in the future. Because of an enormous population, each person is allowed to live on only one given day each week. The other six days people are cryogenically frozen by a process known as "stoning." Since no one ages while stoned, a person who lives to be 80, biologically, has actually survived for 560 years, but only on Tuesdays, or whatever his one day happens to be.

Jefferson Caird violates this system. Refusing to stone himself, he becomes a daybreaker, breaking into the worlds of the other days. To escape the tight surveillance by the Dayworld police, he develops an ability to create a completely different persona for each day. Tuesdays he's a policeman, Wednesdays a bureaucrat, Saturday a religious zealot, and so on.

Dayworld is so crammed with personas, subplots and the labyrinthine logistics of Farmer's universe, that readers never had a chance to become involved with the story or get to know the characters. Fortunately in Dayworld Rebel, Caird forsakes his multiple personalities to become simply William St.-George Duncan. As Duncan he escapes imprisonment and flees to the "great forests of New Jersey" where he joins a rebel band. Its leaders assign him and two colleagues, Cabtab and Snick, to the state of Los Angeles where they are to infiltrate the establishment and collect information helpful to the cause.

Cabtab is a delightful, gigantic, Buddhaesque figure who pantheistically espouses the teachings of Allah, Thor, or any other deity that comes to mind, but his soul is pure pragmatism.

Snick is Duncan's love interest. In one of Farmer's most evocative scenes, he finds her "stoned" in a government warehouse that stores millions of frozen citizens lost forever in the embrace of synthetic death. Duncan destones Snick, who turns out to be one hard-fighting, sexy gal.

Together this engaging trio learns that they can trust only themselves. Forced to escape from one high-tech trap after another, they search for answers to a bewildering array of questions about an insane world that changes its entire population daily.

Who really runs the government, and who controls the rebels? Why is Duncan the only person who can lie when sprayed with the dreaded truth mist? And what about the the Immers, a small covert sect who hold the secret to eternal life?

Farmer keeps Dayworld Rebel awash with plot twists, but by keeping firmly centered on his amiable trio of heroes, he avoids the turgid blizzard of structural complications that so overwhelmed Dayworld.

Genetic Invention

JUST THE THOUGHT of genetic engineering sends chills up most people's spines, conjuring up images of two-headed calves and Nazi experiments. It is the line of Nature that Science must not cross.

In Dawn (Warner, $15.95) Octavia Butler creates a scenario in which humankind must either accept genetic tampering or perish. And the tamperers are not scientists, evil or otherwise, but a race of monstrous looking extraterrestials known as the Oankali. The Oankali survive through trading genetic ma erial with other intelligent species, altering both sides forever.

All the elements are here for a good, old-fashioned laser-'em-up with mankind valiantly defending its right to stay human -- a kind of cosmic "I Gotta Be Me." Butler, however, chooses another route entirely. Her heroine is no hard-as-nails, alien-fighting Sigourney Weaver, but Lilith, a resilent, intelligent, questioning young woman.

And the Oankali, for all their monstrous looks, are a thoughtful and keenly perceptive species, with a highly developed value system. They have brought survivors from Earth's nuclear war aboard their ship, a huge craft that is a small world in itself.

The Oankali quickly realize the potential humans have for violence and irrational behavior when confronted with the unknown. They choose Lilith to be their ambassador to the others, to prepare them to accept their circumstances, which, the Oankali say, includes eventual return to Earth.

But first, Lilith must endure a long arduous process of learning about the Oankali and accepting that mankind's future lies in the tentacles of these grotesque-looking aliens. To help her adapt, they assign Nikanj, an Oankali child, to be her teacher and constant companion.

Lilith and Nikanj forge a relationship that is at once moving, frightening, funny and earily beautiful. At first, the two are wary of each other. Soon Nikanj finds it must alter Lilith's brain chemistry to give her a more powerful memory to help her learn. Afterwards Nikanj says, "I was afraid I could never convince you to trust me enough to let me show you what I could do -- show you that I wouldn't hurt you. I was afraid I would make you hate me." Despite unearthly knowledge and tentacle-covered body, Nikanj is still a child with a child's need to be loved.

Lilith becomes the object of the other humans' suspicions and distrust, as well as her own self-doubt. Is she saving her fellow human beings or betraying them? Butler leaves the question open, but the bond that is forged between Lilith and Nikanj is so touching and so essentially right, that it transcends all else.

And We Are For the Dark

IN HIS FIRST novel, The Damnation Game (Putnam, $18.95) Clive Barker plunges straight to hell with a remarkably powerful portrait of post-war Warsaw. The nightmare is not of mere destruction, for Barker also evokes the much more horrible imagery of a teeming and utter decadence that seems to ooze from the rubble of the city.

Here the Thief and the Cardplayer meet, two fable-like characters who begin their hideous game that lasts for 40 years.

Abruptly Barker pulls us into present-day London. the Thief is now Whitehead, the elderly head of a multi-million dollar empire. He has betrayed the Cardplayer, Mamoulian, and now fears his vengeance. And well he should, for Mamoulian has survived for more than 200 years, and his powers include reanimating the dead who serve as his bond slaves.

Chief among Mamoulian's minions is Anthony Breer, a resurrected child mutilator whose slowly decomposing body slouches inexorably along, carrying out whatever filthy, hideous tasks his fastidious master commands. In Breer, Barker has created a truly legendary monster.

Caught in the middle of Barker's constantly escalating carnage are two relative innocents, Whitehead's heroin-addicted daughter and his young bodyguard, just paroled from prison. They are mercilessly used as pawns by both sides in their vile game of obsession and revenge, suffering through an incredible series of unspeakable acts.

Time after time Barker makes us shudder in revulsion. In pure descriptive power there is no one writing horror fiction now who can match him. And to his credit, Barker does not write in a social vacuum. His terrors arise, at least in part, from a profound sadness and misery he perceives in the human condition.

However, there are only so many unspeakable acts one can speak about. No matter how brilliant the language, many readers will eventually be numbed by Barker's excess. His overkill deprives us of a sense of anticipation, and without anticipation there is no suspense.

Both here and in his six volumes of stories, The Books of Blood, Barker has proven that he is a master of horror who has yet to write his masterpiece.

The Touch of the Master

THIS COLLECTION of macabre tales by veteran horror writer Robert Bloch, author of Psycho, is just the thing to while away those sleepless summer nights.

But you say you don't want nightmares. No problem. Midnight Pleasures (Doubleday, $12.95) is designed more for giggles and the occasional tiny tingle to the spine than for any real teeth-rattling horror.

Bloch's stories all follow a formula. The hero's got trouble, and we know it right from the start. It might be an adulterous artist lusting after his model as in "The Night Before Christmas," or one more poor soul who thinks he can out-maneuver the Father of Lies as in "Picture," which opens so delightfully with the sentence, "Farley found the devil through the Yellow Pages."

The rest of any of these stories is just a set-up for an ironic twist, the unforeseen turnaround at the end. Bloch strives for that perfect coup de grace to be delivered, almost always, in the very last sentence.

When they work, Bloch's endings afford a satisfying little thrill of evil pleasure. Other times you'll cry, "Bah, I knew it from the start!" But no matter. There's no reason to linger. Just turn the page and gobble up another goodie.

The Heart Has its Reasons

THE PROMOTIONAL release from the publisher of Ramsey Campbell's Scared Stiff: Tales of Sex and Death (Scream Press, $25) warns the retailer not to sell to minors. Yet while the stories do contain explicit sex, they are no more graphic than what one might encounter in the latest steamy, supermarket paperback.

Instead Campbell offers seven skillful tales of suspense that employ horror and eroticism to illustrate the terrible desperation born of unnatural sexual repression and simple loneliness.

The scenarios range widely from a 17th-century Salem-like town complete with witches, covens and orgies to a contemporary London paperback cover artist who obsesses over the sexual violence depicted in his own work. Central to each, however, is a lonely anti-hero who can share neither love nor sex -- at least not in any normally accepted manner.

The centerpiece is "Stages," a riveting tale of a voyeuristic hippie-sculptor who pops some mutant LSD, enabling him to control the sexual behavior of the lovers on whom he spies. Breathlessly told, the story mounts to an exquisitely horrifying conclusion. J.K. Potter illustrates, but his abstract collage style, combining drawing with photography, is inappropriate for Campbell's very personal, very human stories.

Laurence Coven, author of "Where There's a Will, There's a Murder," frequently reviews science fiction and fantasy.