BOONE By Brooks Hansen and Nick Davis Summit Books. 394 pp. $19.95

The parts you remember most warmly about this too-ambitious first novel by a couple of young New Yorkers are the sections set back in Southern California in the mid-'50s, a decade before the authors were born. Eton Boone, the iconoclastic American theatrical "genius," whose short, fast life this "oral history" examines, is growing up with his mother, Blue, a painter whom he adores, and his father, Joe Boone. Joe, an otherwise decent-natured radio executive, is unfaithful to Blue while she is dying of cancer, and this becomes the central wounding event of Eton's youth and the wellspring of the rage that drives his art.

As in such documentary-style nonfiction books as "Edie" and "Haywire," Brooks Hansen and Nick Davis's "Boone" is composed of anecdotal sketches by people who knew the main character, and before Blue's decline and Joe's betrayal, there are some wonderful snapshots of a lively, complicated family in an innocent time. Levi Mottl, a painter and New Yorker to the bone, recalls finding placid San Diego "a town out of a dull person's imagination" until he meets Blue and learns to see Southern California the way she does. "I used to come over to the house, and Blue would take me out to the back yard. She'd stand out there and it was like watching her bloom. There was a lemon tree and the yard wasn't very big. It faced the ocean, just a half mile down the hill, so there was always a light salt in the air. At dusk the clouds would get a sort of salmon color, and the shafts of light would spill through the leaves of the lemon tree and shift in the breeze. The house was stucco and Blue would point at the shadows on the white face and say how azure they were, to match the sky. ... And when the lemons were out in summer, they'd glint in the twilight. The yellow could just stain your eyes."

The grown-up Eton, who paints in addition to writing, directing and performing, learned from Blue how to appreciate color and light. When he meets his friend-to-be Amalie Hindemuth on a bench in Paris, she removes her shades to show Eton her hideous black eye. Eton, fascinated, tells her, "It may not be right for faces, but that's a hell of a color, Amalie." Whenever the talk that makes up "Boone" is about painting -- about seeing -- it's evocative and affecting.

A lot less successful but still interesting -- this is a novel that slides downhill in a graceful arc -- are the sections set in New York City in the late '60s, when Eton makes his reputation as a comic performance artist by doing savage extended impersonations of cultural icons. An amalgam of Robin Williams, Rich Little and Lenny Bruce, Eton improvises a hilarious new evisceration each night at a club called Jes' for Laffs. He does the usual putdowns of Sammy Davis, Hugh Hefner, Jerry Lewis, Diana Ross et al., then goes on to savage J. Edgar Hoover, Timothy Leary, Roger Vadim, a grotesquely "hollow" Laurence Olivier and, among others, Tony Bennett entertaining at a roadside camp on the march to Selma. Not only are these routines, as transcribed, not all that funny or convincing -- was Tony Bennett's civil rights support mere show biz grandstanding? -- but since we can't see them we have to take each witness's word that these were exhibitions of genius. There's no evidence of greatness in the novel, inevitably maybe, since the protagonist is Eton Boone and not, say, William Butler Yeats.

Still unhinged after many years by his father's infidelity and his own complicity in it, Eton comes close to a psychotic break during his more sadistic performances and eventually goes over the edge. He ridicules an old-time stand-up comic named Bert Nieman so viciously that the old man stabs himself in the stomach -- onstage. The scandal sends Eton off to England, where the novel, only half done, sinks. A lot happens but it all feels arbitrary, more incidents showing Eton's eccentricity, callousness and purported greatness. Eton writes and directs a cine'ma ve'rite' treatment of Beethoven going deaf. Again we don't get to see it. Back in the United States, Eton writes a play about two painters, one based on his mother. He has an affair with his stepbrother Hilary -- a beautifully sculpted sad case whose way of presenting himself to the hundreds of men and women he seeks acceptance from is: "I have a present for you. Moi." Eton drops Hilary and has an affair with the actress playing his mother -- no big deal is made of this. He writes a novel. He mourns when the actress dies in a fire. In 1975 Eton dies when he runs his motorcycle into a truck, maybe accidentally, maybe not.

We don't know what's on Eton's mind when he dies, or at any other time, for the straitjacket form the authors have used in limning their hero prevents it. In the drone of chatty reminiscences, Eton comes across in the end as not much more than an egotistical bore. You miss the boy back in San Diego and wish the whole novel had been about him, and Blue, and Joe Boone. Claire Sullivan, a family friend, recalls: "Blue's father used to have an expression. ... He'd say if people were trees, most of them wouldn't even be honest enough to lean towards the sun ... but Blue found a man who would. She always said Joe leans toward the sun ..." Except, of course, when he didn't, a story maybe more compelling and believable than the one the authors chose to tell. The reviewer writes frequently about contemporary fiction.