The novel has a tiny companion volume, the hastily produced "Gumpisms: The Wit and Wisdom of Forrest Gump." At 1,600 words, it has more white space on its 88 pages pages than there is between Forrest Gump's ears. Yet nuggets like "Don't lick nothin' that sticks to your tongue" will make it No. 1 in the "advice and how-to" category on Sunday, with 500,000 copies in print. Surely readers will not mind that Mr. Groom, under a tight deadline, did not have time to write all the Gumpisms himself and had to press his editors into service. Son of Forrest Gump

Pocket Books, the publisher of both books, plans to reissue three of Mr. Groom's other novels and has signed him up to write a Gump sequel, to be published next year. "It will be about Forrest and Forrest Jr.," said Mr. Groom. "I'm interested in the relationship between this certifiable idiot and his son, who is very smart. And since the first book ends in 1980, that leaves me about 15 years' worth of stuff to make fun of."

As Mr. Groom tells it, pretty much everything about the Gump phenomenon has been a surprise to him, including the writing of the novel. The germ of the book came to him when his father, a lawyer in Mobile, Ala., began reminiscing one day about his childhood, and about a slow-witted boy in the neigborhood whose mother taught him to play the piano. At about the same time, Mr. Groom said, he saw a segment on "60 Minutes" about idiot savants.

"I thought that was a good idea for a character," he said. "By midnight the first chapter was already written." Six weeks later, the novel was done. "It wrote itself," said Mr. Groom. "It's almost like the lizard part of my brain went into gear and bypassed the brain up here." Mr. Groom pointed to his forehead. "It will never happen to me again."

The result was an unusual blend of farce, satire and the picaresque, told in Forrest's voice. Fans of the movie may be surprised to find out that in addition to being a champion Ping-Pong player, the Forrest of the novel is a professional wrestler, a chess grandmaster and an astronaut. He smokes marijuana and makes friends with an orangutan in New Guinea. In Hollywood, he lands the title role in a remake of "The Creature From the Black Lagoon," starring Raquel Welch. From Respectful to Raves