KEEPING WATCH A History of American Time By Michael O' Malley Viking, $19.95 Nonfiction

In 1826, New Haven's town fathers paid Eli Terry, Connecticut's most celebrated clockmaker, two hundred dollars to install a clock in the town hall. They wanted a proud symbol of their commitment to order, regular habits, and the virtue of conserving time, and at first the clock served them well. But soon they noticed a growing disagreement with their other source of public time, the Yale College clock. Gradually Terry's clock fell farther and farther behind its rival-five, ten, then fifteen minutes. Perhaps it only needed adjusting. Then it slowly began catching up, raising hopes that it might settle down into steady work as it matured. But instead with each passing day it moved ahead of Yale's timepiece. Finally, almost fifteen minutes faster, Terry's perverse clock began sinking back into its old slothful habits, only to once again start gaining on the old faithful college clock, week by week. Had Terry saddled the city fathers with an incompetent timekeeper, or some reckless whimsy?

MAX LAKEMAN AND THE BEAUTIFUL STRANGER By Jon Cohen Warner Books, $16.95 Fiction

Max Lakeman, ever the alien, sat in his lawn chair in the thin shade of a dying peach tree, watching his family. Who were these creatures? How had they gotten into his backyard? What did they want?

One of the two smaller creatures turned and looked across the lawn at him. It had spotted him. Contact was imminent. It spoke, startling Max with its command of the Earthling language. ''Daddy. Come play.'' Daddy? ''Max. Get the ketchup and relish, will you?'' his wife, Nelly, called to him. ''The burgers are about done.'' Ketchup? Relish?

TOO GOOD TO BE TRUE The Outlandish Story of Wedtech By James Traub Doubleday, $21.95 Nonfiction

< John Mariotta was a short, squat man with a disproportionately large head made larger still by a wavy crest of pomaded black hair. ''Banana Head,'' Fred Neuberger used to call him, in one of his fonder locutions. He wore, at least until he underwent a sort of corporate makeover in the early eighties, thick black glasses, long sideburns, and short, wide ties. But nothing was so strange about John Mariotta as the matter and manner of his speech. He was extremely excitable, and he spoke in a wild stream of words, his voice getting higher and higher and thinner and thinner until he seemed almost to be choking.

MASQUERADE By Janet Dailey Little Brown, $19.95 Fiction

She sipped at the wine in her glass and watched with marked indifference the lewd gyrations of a short, fat man garbed in the costume of Bacchus, a wreath of grape leaves encircling his bald head and a toga stretched tautly across his protruding stomach. His partner wore a simple black cocktail dress, a collection of ribbons and bows in her hair, and festive makeup that included glittering pink eye shadow and blue stripes on her cheeks. Near them, a woman in a high, powdered wig, a fake mole, and a gown from the court of Louis XVI danced with a man in a red tuxedo with devil's horns in his head.