Towel? Check.

Coppertone? Got it.

Hefty book in which a rich person, preferably socially prominent, slaughters a member of his or her own family?

It's likely to be as much a beachgoer's staple this summer as zinc oxide. Publishers have earmarked hundreds of thousands of promotional dollars to entice hundreds of thousands of readers to curl up with one of several lively accounts of mayhem among the mighty.

"People enjoy reading about rich people who have done horrendous things," says Betty Prashker, editor in chief of Crown, which has just ordered a second printing (the first was 50,000 copies) of Dominick Dunne's "The Two Mrs. Grenvilles."

"It's very reassuring. I had grown up thinking that there were one or two situations that occurred in my own family that were strange, but having read these books I can see that my own family was a model of probity and happiness," Prashker elaborates. Having edited Tommy Thompson's 1976 best seller, "Blood and Money," the progenitor of the current crop, gives her theory a certain weight. "People who live mundane lives find it liberating to see that people they might have envied have had unhappy, difficult lives that ended in total tragedy."

Dunne's protagonist, for instance, is a blond Kansas chorine who marries into a blueblood family, claws her way to respectability, then blows her husband away with a double-barreled shotgun, escaping conviction by claiming that she mistook him for a prowler. The book is a novel which, Prashker gleefully points out, means it won't have to compete for a slot on best-seller lists with the three other society murder yarns, all of which are nonfiction.

But Dunne, a film producer and brother of writer John Gregory Dunne, modeled his novel on the 1955 Woodward case, going so far as to visit the house on Long Island where Ann Woodward shot her wealthy husband.

Slugging it out in the nonfiction arena are the two epics about 17-year-old Marc Schreuder's murder of his grandfather, Franklin Bradshaw, a Salt Lake City multimillionaire, at the behest of Frances Bradshaw Schreuder, the victim's daughter, the murderer's mother.

One could argue that the Utah murder doesn't exactly qualify as a society slaying. Bradshaw's was "a fortune made in used auto parts in the last 10 minutes," sniffs one East Side partygoer and observer, proving that status matters even in murder. "That's not society, that's money, uninteresting money. No one knew them." Still, Frances Schreuder was a benefactor and board member of the New York City Ballet and maintained the requisite Manhattan co-op and Southampton retreat. And there are enough sordid family secrets in the tale to reassure readers of the superiority of their own lives.

The sniping about which book is the true heir to Tommy Thompson, who had contracted to write the saga but died in 1983, and about whether author Shana Alexander indulged in checkbook journalism (her publisher paid Marc Schreuder for the exclusive rights to his story) has only set off a valuable wave of publicity. Atheneum has ordered a 50,000 first printing of Jonathan Coleman's "At Mother's Request -- A True Story of Money, Murder and Betrayal"; Doubleday has printed 100,000 copies of Alexander's "Nutcracker -- Money, Madness, Murder: A Family Album" and is budgeting $100,000 for promotion.

And coming soon to bookstores everywhere, "Savage Grace," the book with the best blurbs (Mailer, Doctorow, Buckley). "Savage Grace" offers both matricide and incest among the Baekelands, another wealthy and gorgeous New York clan bankrolled, in this case, by an immigrant patriarch who invented Bakelite, the first successful synthetic plastic. William Morrow has a 50,000 first printing waiting to hit the shelves.

"Tragedy is always about people who are larger than life -- kings and princes, not bus drivers," says Steven M.L. Aronson, coauthor with Natalie Robins of "Savage Grace." Aronson knew Barbara Baekeland, who was murdered by her son, and drew on her letters in writing the book.

"The Baekelands were rich, educated and intelligent, dazzling-looking. They're the favorites of the gods, those of whom the most would be expected. When they fail, they fail spectacularly."

Whatever psychic needs they may fill, these bluebloody tales will not fade with readers' tans. Paperback rights to the Dunne, Coleman and Alexander books have already been sold, in each case for what publishers call "six-figure" sums, and "Savage Grace" has a six-figure floor, meaning that Morrow will not sell it to a paperback house for less.

Don't forget the mini-series. All four books have been optioned for television: Lorimar's bought "The Two Mrs. Grenvilles"; CBS picked up the Coleman book and NBC/Warner has commissioned a script for "Nutcracker"; ABC and producer Stan ("Roots") Margulies are planning a five-parter of "Savage Grace."

And then next spring, just when the reading public is ready for a nice diet book, get braced for the next wave of the tofficide genre -- the von Bu low books. Claus von Bu low himself has completed a major portion of a manuscript; Boston Herald reporter Alan Rosenberg is looking for a publisher; Crown is discussing the possibility with Dominick Dunne, who covered the trial for Vanity Fair; and there may well be others. Then there will surely be paperbacks of those books, and probably mini-series, and so on. If Shakespeare were still in the business, added a little sex and got a good agent, he could probably have a hit with "Hamlet."

"We know from 'Dynasty,' " notes author Aronson, "that we all like to see the rich and famous screw up."