WHY ISN'T THIS book funnier? Humor is mentioned on the dust jacket, where the publishers further advertise it as "a symphony of the supernatural in four movements." It is in fact pasticcio, a suite of four pieces parodying four fiction genres. Only two of these stories have any supernatural elements whatever.

The four include a hard-boiled detective story involving a vampire, a western incorporating a ghostlike gunfighter, a manor house gothic, and a white-queen jungle adventure. So of course the whole package is marketed under the Doubleday Science Fiction imprint. Evidently the theory is that one genre is pretty much interchangeable with another.

Alan Ryan goes some way toward proving this theory, by grinding out stories as different and distinctive as four strands of spaghetti. Did he write them, I wonder, to settle a bet? No other intention is apparent.

The bet could be: is it possible to wring one last laugh out of any of these moribund genres, which have been worked over by everyone from Abbott & Costello, Mel Brooks and Roman Polanski on down to the "creators" of animated cartoon features for Saturday morning TV. Still, there's always one wheeze left in the corpse, if you know how to squeeze it.

Or one drop of blood. In the first story, "Kiss the Vampire Goodbye," private investigator Mike Kendall helps his client, Mary Cantrell, find the vampire that has killed her father. Kendall, a detective who refuses to wear a hat and keeps a flask in his shoulder holster, is assisted by an albino Eskimo. After eating a few hamburgers, they clean up the vampire problem.

In "The Man Who Killed Forever," a retired gunfighter named Clayton Bannister finds he must go up against a black-clad villain named Siempre who takes over the town. Bannister is assisted by old Jed Tree and young Billy Wagner, and by a woman named Mary Cantrell (for it is she). Before he finally guns down Siempre, he spends a good part of the story looking at sunsets, cacti, etc., all of which is recorded in greatly padded detail.

Amanda Rutherford, in "Candlewyck," goes to the gloomy house of that name to act as lady's companion -- but to whom? The satanically handsome Mr. Paget- Poole won't say. What are his intentions? And what of his deformed and birthmarked servant, Crickback? Amanda finds herself a prisoner, intended for a fate worse than death -- as explained by her fellow sufferer, Mary Cantrell (for it is she). Paget-Poole means to sell their favors to men. Assisted by Crickback, they set the house afire and escape.

"The Queen of Kilimanjaro" introduces the members of the Adventurers Club: Sir Clive Waterstone-Foyle, Col. Sir Maurice Heywood Witherspoon, and others. In 189-they set out to rescue a white woman captured earlier by dusky savages. They are assisted by Ngugi wa Babatunde and several bearers. The villain is Ngugi's evil brother, who is found on the verge of marrying Mary Cantrell (for it is she). She is rescued from this unspeakable fate. Then, as at the end of each story, she drifts away.

THE INVENTED funny bits aren't so funny. One of the best occurs in "Candlewyck," when prisoners Amanda and Mary are preparing to make their escape. Amanda has a moment of doubt (original italics):

"Suddenly the task -- and therefore our entire plan of escape! -- seemed utterly impossible. We would never break through the wall using only a knife and fork!"

Few of his comic characters are comic: The notion of a 300-pound albino Eskimo named Danny Lavender never gets remotely funny, and serves no other conceivable purpose except possibly to win another bet. Much funnier is Colonel Witherspoon, who conveys all of his thoughts, feelings, and opinions by clearing his throat.

The borrowed material fares not much better. The idea of a London gentlemen's club where the members are forbidden to speak to one another was no doubt sidesplitting a full century ago when Conan Doyle cooked it up; it has since been borrowed by everyone from Dorothy Sayers to (I'm ashamed to say) me. Can there really be any fun left in it?

Parody aside, Ryan could have had fun with recurring symbols -- but didn't. True, the detective says the city is a jungle, and three stories later, the jungle is a jungle. True, moonlight and roses recur. But the great defining symbol is Mary Cantrell. She turns up in all stories as a woman with sparkling dark eyes, and no other noticeable characteristics or character -- something like a body that keeps falling out of different closets.