BOOK REVIEW : Homage to the Dwarf Who Played E.T. : MAYBE THE MOON, <i> by Armistead Maupin,</i> HarperCollins, $22; 305 pages

One thing is sure: “Maybe the Moon� is never going to be one of Steven Spielberg’s favorite novels.

Armistead Maupin has put together a fictionalized homage to Tamara de Treaux, the young female dwarf who--much of the time--inhabited the suit of that lovable extraterrestrial, E.T.

Maupin has also written a traditional Hollywood novel, shimmering with literary echoes of every kind: the artificial grass of Fitzgerald’s “The Last Tycoon,� the colloquial diary style of Gavin Lambert’s “Inside Daisy Clover� and Anita Loos’ “A Mouse Is Born,� and, of course, the midgets and dwarfs who drifted through Nathanael West’s “The Day of the Locust.�

This time the dwarf is not a grotesque character seen from afar but the writer of the diary, the narrator of the book. Cadence Roth (Tamara’s fictional presence here) is pushing 30 but still living off memories of her one big cinematic break.

Ten years before, in the early ‘80s, she played Mr. Woods in the movie of the same name--a treacly tale about a little boy in a tract house who discovers a lovable elf in his back yard. Part of the time that elf was mechanical, but part of the time the elf was Cadence Roth, sweating like a galley slave in a wired-up rubber suit.

The producer, Philip Blenheim, has sternly forbade Cadence from talking about her role, so as not to detract from the “magic� of the film.

*

Ten years later, Cadence has fallen on hard times. She has been reduced to playing cold cream jars in “infomercials.�

Her plucky, protective mother has died, but she’s been lucky enough to latch on to Renee, a buxom blond airhead with a golden heart who takes care of her. The two of them now live in the San Fernando Valley, on the margin of Hollywood life. Cadence knows that her agent dreads her calls. The thing is: Cadence is the world’s shortest ambulatory human being--except for some tiny upstart in Eastern Europe. But beyond that, Cadence knows she has talent. She’s an actress; she’s a singer.

In one of life’s dizzy sweeps, Cadence runs into Callum Duff, the man who once played the little boy in “Mr. Woods.�

Callum is gay and involved with one of Cadence’s own best gay friends, a vulnerable dear heart whose former lover has died of AIDS. And--down and out--Cadence joins a dubious troupe of performers called Porta-Party, who go to birthday parties for Hollywood doctors’ children--all of those striving middle-class folks who need to have a little better party than anyone else’s.

It’s a heckuva job for a dwarf, but it’s the only one around. Plus, the troupe is run by Neil Riccarton, a tall, handsome black man who’s plowing through a bad divorce.

Life isn’t supposed to be like this. Callum Duff is supposed to go out with bimbos instead of guys. Beautiful Neil should fall for Renee, but instead it’s he and Cadence who end up sharing a magic weekend on Catalina Island in adjoining musty rooms at the Zane Grey Hotel. (An echo of one of the most obscure of all the novels in this genre, “Pollyanna in Hollywood.�)

The thing is: Cadence is living on borrowed time and on the flimsiest of dreams. As a dwarf, she has a short life span. She has more in common with the man who died of AIDS than anyone else in this story.

She must believe in her talent and in the power of affection; she must try as well to reclaim her identity as an actress. It was she in that Mr. Woods rubber suit, just as Tamara de Treaux gave life to E.T. It’s not fair to work and love and perform and not be rewarded for it.

*

Here, Armistead Maupin starts tying up threads. This is a white heterosexual world we live in, he insists. There are big bucks involved in Philip Blenheim’s vision of sanitized suburbia. The intelligent dwarf with an active sex life had best stay in her wet suits.

And--despite Rock Hudson and all that recent history, handsome leading men are supposed to fall in love with pretty leading ladies , not other handsome men. All this material goes down in Cadence’s diary. She sees her life. She worries about her weight and occasional shortness of breath. When her love life is dealt an awful turn, she handles it. What she wants is to be human and, in writing, she does prove her own humanity.

Meanwhile, the Philip Blenheims go grinding on, churning out odious greeting-card dreams.