BOOK REVIEW / FICTION : A Resonant Warning on the Price of Fame : MEN IN BLACK, <i> by Scott Spencer</i> , Knopf, $24, 336 pages

“No man but a blockhead ever wrote except for money,” said Samuel Johnson, though Sam Holland, the beleaguered hero of this diverting and eerily timely novel, might disagree, especially after his current adventure in commercialism.

As a promising young author, Sam produced a few well-received but unprofitable books, but now, as a 40-year-old husband and father, he’s been obliged to augment his income by cranking out whatever trendy nonfiction his publishers assign. Using a pseudonym, he’s written “Traveling With Your Pet,” “An Intelligent Woman’s Guide to Pro Football” and “Crystal Death,” an expose of the perils of salt.

His newest and riskiest venture in this genre is “Visitors From Above,” a scissors-and-paste job about creatures from outer space, assembled from the vast but highly dubious literature on the subject. His publisher has run off the usual 7,500-copy first printing, expecting no more than the modest response that has greeted Sam’s other efforts.

Everyone is astonished when “Visitors From Above” takes off like a UFO, attracting a public Sam hardly knew existed. From restless anonymity in the small Hudson River town of Leyden, N.Y., Sam is suddenly catapulted into national prominence as John Retchliffe, expert on close encounters of the third kind. Overnight, he’s the darling of a coterie of true believers, people with whom he has less than nothing in common.

By a fluke too bizarre to bear examination, the nom de plume he has chosen just happens to be identical to the name of the man who wrote the infamous “Protocols of the Elders of Zion,” the vicious anti-Semitic tract distributed by extremist hate groups. Now these people have become Sam Holland’s admirers, standing in bookstore lines with cash in hand, a bitterly ironic coincidence calculated to drive a liberal, well-intentioned man entirely over the edge. These fans read his book backward and forward, deriving extra-terrestrial messages from the first letters of each paragraph, welcoming him as one of their own, even identifying him as an emissary from space.

Driven by economic necessity, the Holland family--Sam; his wife, Olivia; their 14-year-old son, Michael, and their younger daughter, Amanda--has recently left Manhattan to live in Leyden, a move that has seriously strained the already precarious family tranquillity. An hour and a half from New York, Leyden is more backwater than exurb, and Michael loathes it. The fact that Sam is now being shipped around the United States on the publicity tour from hell has aggravated Olivia’s loneliness and her well-founded suspicion that Sam may have had a fling with a young woman who helped with his UFO research.

Virtually every writer has a harrowing tour story or two, but Sam’s experiences on the road are uncommonly hilarious and terrifying, handled with tremendous verve. In addition to the usual rigors of such tours--abrasive talk-show hosts, lunatic call-ins and a grueling schedule of dawn-to-midnight appearances, Sam must impersonate a man who truly believes every outlandish tale in the book, a personality utterly alien to his own.

Though undreamed-of sums are rolling in, prosperity is only exacerbating the Holland family’s problems. Bored and resentful, Michael finds a compromising love letter among his father’s papers. Unable to deal with his discovery, he runs away in a desperate effort to attract his parents’ attention, succeeding only in intensifying their difficulties.

The change is radical. From an average sullen teen-ager, Michael abruptly becomes an outlaw, living in the woods with a gang of thieves. Frantic with worry, Olivia goes berserk, vandalizing their house while Sam is away on his publicity tour. Until that moment, she had seemed both dauntless and resilient.

While both these personality switches tax the readers’ credulity, they do serve as powerful commentaries on the price of fame. The melodrama may be somewhat excessive, but without it, “Men in Black” would neither be as resonant nor as apropos as it is. In addition to acute observations on the hazards and vagaries of the literary life, the novel examines the effects of chronic insecurity upon a family of intelligent, well-meaning and generally agreeable people. The result is funny, sad and by no means impossible.