Forgive me for saying so, but being the author of Forrest Gump (the novel) must have been a very Forrest Gump (the movie) sort of experience. You write this unpretentious, reasonably funny little satirical novel that doesn’t get a whole lot of attention at first. Hollywood buys the movie rights for what wasn’t a big pile of dough — $350,000, to be exact. Then eight years later it becomes the biggest, most beloved film of 1994.

So you become a little bit famous, and there’s a paperback deal — except they put Tom Hanks’ name on the cover a whole lot bigger than yours. And talk about your box of chocolates, get this: Studio accounting reportedly shows that even though Gump (the movie) has grossed nearly $700 million worldwide, it’s actually lost money, and you, Winston Groom, have to hire an attorney to prod Paramount into giving you the extra $250,000 you feel you have coming to you.

As I say, it’s a Forrest Gump kind of experience. So what do you do? Well, if you’re smart, you decide to write a sequel: Gump & Co.. Then if anybody decides to make Gump II, the movie, they’re going to have to deal with you. But do you write a sequel to your book or to the film? As so often happens in Hollywood, they’re really quite different. The original Gump, after all, wasn’t a warmhearted dope like Hanks’ character, but an idiot savant like the one Dustin Hoffman played in Rain Man — a 6-foot-6-inch, 240-pound musical genius and walking computer, who’s also, to be frank, a bit of a redneck.

Imagine Huck Finn suiting up for the Alabama Crimson Tide back in the late ’60s and running the ball into ”a pile of Nebraska corn shucker niggers an big ole white boys” and you’ll have the basic idea. (Not that anybody’s ever going to confuse Winston Groom with Mark Twain.) In Groom’s original book, Gump’s Vietnam pal Bubba wasn’t black; he was white. And Jenny didn’t latch on to Forrest just because he was so sweet-natured but because he was hung like a Clydesdale stallion. Gump didn’t lose her because she ran off with hippies; he lost her because, among other things, he threw his Congressional Medal of Honor during an antiwar rally and injured a politician — and was summarily hauled off to a mental hospital. And Gump didn’t invent jogging; he became a pro wrestler.

For that matter, Groom’s occasionally bitter satire isn’t chockful of such heartwarming maxims as ”Life is like a box of chocolates,” or ”Stupid is as stupid does” — which is not to say the film betrayed the book. If the cinematic Forrest Gump is more sunny and downright sentimental than Groom’s novel, it’s also far richer, more densely imagined and emotionally resonant.

For the sequel, Groom has evidently decided to split the difference. In Gump & Co., our hero’s no longer an idiot savant — merely the feebleminded hero of a limp, episodic tale that aspires to satire but barely rises to sitcom level. Successful satire requires both wit and whimsy, of which this plodding, mechanistic tale hasn’t a trace. Once he’d conceived the project, it must have taken Groom all of 15 minutes to write an outline.

So the public wants to see Forrest in some more computer-enhanced news-reel footage? Groom gives us a moron’s-eye view of what’s basically CNN’s Greatest Blunders of the Reagan and Bush Years. Gump suits up for the New Orleans Saints (one of pro football’s worst teams at the time), turns up in Atlanta to help botch the secret formula for New Coke, visits Iran as ”special assistant for covert operations” under Col. Ollie North, plays Goliath at Rev. Jim Bakker’s Bible theme park, becomes vice president of insider trading for ”Ivan Bozosky,” pilots the Exxon Valdez, accidentally causes the fall of the Berlin Wall, captures Saddam Hussein for ”Gen. Scheisskopf” — even meets Bill and Hillary on a camping trip down the Whitewash River.