DON CARPENTER IS in a perfect position to write about Hollywood. He's worked there. He knows it. He's of it but not in it. (According to the dust jacket, he is now living in Mill Valley, that oasis of hip in Marin County.) There is perspective to be found in physical distance. Partly as a result of this, nobody around today writes as skillfully and authoritatively about the crazy world of movies and show biz as Don Carpenter. He is doing for present-day Hollywood what Daniel Defoe did for 18-century London -- charting its licit and illicit commerce, exploring its underside, revealing in precise detail how the place works. He began with a few fine stories in The Murder of the Frogs, continued with the True Life Story of Jody McKeegan, and now offers another chronicle of life in movieland with A Couple of Comedians.

The book is about just what it says. Carpenter presents the comedy team of Larson and Ogilvie not so much in full-length portrait as in a series of quick, candid snapshots. David Ogilvie is the narrator here. His partner, Jim Larson, is the straight man, singing songs and making with the patter as Ogilvie mugs ("ogles") and supplies the gag lines that bring down the house. Ogilvie also supplies whatever contact with reality the team maintains. After years of playing penny-ante clubs and trying to make it on television with a succession of flop shows, the two finally have hit big in the movies. Their schedule now calls for them to do a movie a year and a month-long sting at the "Golconda" in Las Vegas. Not exactly taxing -- but still too much for Larson, who is just about ready to flip out as the book begins. What's his problem? The old success-at-last syndrome.

Will Larson go off the deep end or won't he? That's what serves A Couple of Comedians as a plot. Not much, I grant you, but somehow it is all Don Carpenter needs as he propels his two protagonists pell-mell from one bizarre adventure into the next wacky episode.

For example, at almost the precise moment Larson shows up at Ogilvie's ranch to inform his partner that he thinks he's going off his rocker, Grandpa Ogilvie drops dead (of old age) in the orchard. Since the two are by then very high on "Maui Zowie," they decide to bury the old man on the spot and inform the absent Ogilvies that he ran off with the Avon lady. Following a rare do-it-yourself funeral, they set off on a drive down the coast reminiscent of that wild voyage in a Cadillac taken by Sal Paradise and Dean Moriarty in Jack Kerouac's On The Road. They stop off in San Francisco and create chaos at a swanky dinner party from whence they are whisked in a studio limousine to Hollywood, where they are to make this year's movie.

That's where the fun really begins. Or not fun exactly, for let it be put plain: A Couple of Comedians is not so much funny as it is Hollywood-freaky. All Carpenter does is present the place, the milieu, the state-of-mind as it really is. What might seem the most extreme burlesque turns out here to be no more than stark realism. The book offers as accurate a picture of life behind the scenes in show business today as anything I have read since -- well, since The True Life Story of Jody McKeegan. By the way, Jody herself puts in an appearance here, suggesting that Carpenter has embarked upon a kind of Hollywood Comedie Humaine, complete with crossed destines and reappearing characters.

There are marvelous vignetts: a baby mogul's lunchtime visit to Schwab's which causes a near-fatal orgy of showing-off among the assembled show biz schleppers; an orgy of the more commonplace variety at the Hefner mansion; a dinner party for a presidential assistant that is broken up by the loud farts of a guest. In fact, Carpenter covers so much ground so quickly that it is hard to believe the book is so short. I only wish it had been longer. However, by the time it winds down at last to its not altogether surprising conclusion in Las Vegas, the reader knows the people and their world so well that he can hardly claim to be unsatisfied. It is rich, rich food fed at a fast, fast pace.