BEHIND THE SCENES In Which the Author Talks About Ronald and Nancy Reagan . . . and Himself By Michael K. Deaver With Mickey Herskowitz Morrow. 272 pp. $17.95

CONVICTED of lying under oath to a congressional subcommittee and a federal grand jury, Michael Deaver is down on his luck. This book at once is his defense, apology and revenge. It's a dangerous ploy. Much of the book is a rambling monologue, and the former White House deputy chief of staff seems shallow, spiteful and whiny. He says his legal problems stem from kidney failure, high blood pressure and alcoholism, which affected his judgment. He says he had a serious drinking problem the last year he spent "at the right hand of the president."

At other times, when he tells how a poor boy from Bakersfield, the only kid in his school with shoes, made it big in Sacramento and Washington by being loyal and playing the piano, Deaver displays an engaging humility.

Curiously absent from these pages, despite Deaver's claims of intimacy, is a revealing portrait of Ronald Reagan. The reader learns about Reagan what he already knew -- the president hates to fire people until goaded by his wife. The unintentional effect is to make Deaver seem merely a flunky. And if it is true that no man is a hero to his valet, then there are signs here of repressed hostility to the master: Reagan could "go merrily on to other matters. And I was left with {the} pressure."

The first lady as depicted here, however, is a different story.

"She was in the truest sense of the phrase my best friend. There was nothing I could not talk to her about, nothing I did not talk to her about." And: "Nancy and I hit it off from the very beginning. Ronnie Reagan had sort of glided through life, and Nancy's role was to protect him . . .

"She lobbied the president to soften his line on the Soviet Union; to reduce military spending and not to push Star Wars at the expense of the poor and the dispossessed. She favored a diplomatic solution in Nicaragua and opposed his trip to Bitburg. Nancy wins most of the time. When she does, it is not by wearing him down but by usually being on the right side of an issue."

Now, no doubt Nancy Reagan is a pragmatic person, and no doubt she has influence and maybe she is liberal-minded, if that is the right word. It does seem a little late in the day to attempt to turn her into the Krupskaya of the Reagan Revolution. But accepting this information at face value is perhaps not the accurate response. What is really astonishing about this passage -- with its vast over-simplifications of complex issues -- is how Deaver, the consummate image-maker of the Reagan presidency ("I let Reagan have one glass of wine before the debate . . . a little color for his cheeks.") tries so hard to paint Mrs. Reagan in "liberal" and "moderate" hues -- the adjectives are his. And the question naturally arises, why?

The answer must be that in some delusory way Deaver believes he is protecting his "best friend" before the bar of public opinion. The effort is gallant by his lights but misguided. A far better and more loyal way to protect her would be to avoid making any observations of a private nature about his employers at all. It is impossible to imagine, say, Robert Sherwood or Harry Hopkins writing about Franklin and Eleanor Roosevelt in the way Deaver writes about the Reagans: for instance, that Mrs. Reagan held the hand of her beloved father for an hour after his death, or that candidate Reagan fumbled while receiving holy communion in an Episcopal church, Deaver referring to the intinctured Host as "gunk."

When Deaver really crackles is when he appraises -- often shrewedly -- his former colleagues in government:

1980 campaign manager John Sears: "on any kind of campaign, the higher your rank the more likely you are to be dealing with egos, colossal egos, in what turns out to be a not very large compartment. Sears really wanted to run the show. He did not want to share power with anyone and, at bottom, he had little in the way of personal respect for the candidate he served."

Former secretary of state Alexander Haig: "The last I heard he was running for president. My guess is that doing so is a fine way to keep up the price of his speaking engagements."

Attorney General Edwin Meese: "a decent and considerate man, whose weakness is a tendency to get overconfident -- in himself or his abilities, which are multiple. In some ways it boils down to a matter of trust. Meese, a prosecutor at heart, is not by nature a trusting person."

Vice President George Bush: "a strong and caring person who has done a difficult job superbly . . . . I still recall the breakfast the morning the Reagans met the Bushes as the 1976 Republican standard-bearers . . . . Barbara looked Ronald Reagan in the eye and said, 'Governor, let me promise you one thing. We're going to work our asses off for you.' There was nothing she could have said, at that moment, that the Reagans would have responded to more."

Former budget director David Stockman: "He was very facile and quick and impressed everyone with his whiz-kid instincts. He had attended divinity school, at least partly to avoid the Vietnam war . . . . He would prove himself to be something less than a steadfast, trustworthy person. I regret not getting the message sooner." SOMEWHERE along the line, Deaver developed a taste for 1968 Heitz Chardonnay, "the finest white wine made in America." He liked lunching at Maxims in Paris with Pierre Salinger, and he liked being befriended by media moguls and Washington hostesses. "The first year or two, we received some fifty invitations a week. I used to joke that we wore formal clothes so often that my son . . . thought 'black tie' was the name of a restaurant."

He resigned his $75,100-a-year White House post in spring 1985, turned down a job in the "$300,000 range" with the public-relations firm Burton-Marsteller and opened his own consulting firm, Michael K. Deaver and Associates. In no time at all the firm had dozens of clients, including two foreign governments, and Deaver was negotiating its sale to the British advertising and public-relations giant, Saatchi & Saatchi, in a deal that would have brought him $18 million over seven years. At this point, he, says Mrs. Reagan called him to say, "Mike, be careful. I have a feeling this is happening too fast."

The new affluence and Deaver's vaunted access to the highest government circles did not go unnoticed, and a special prosecutor was appointed to investigate allegations that Deaver violated the federal ethics act. The investigation that followed led to his conviction last month on charges of perjury. As far as Deaver is concerned, he is innocent, though he admits, "Of course I am guilty of being careless of appearances." And, "I can look back now and see that I was careless, stupid, inattentive to the enemies I had made.") He notes of the special prosecutor, Whitney North Seymour Jr., "As a Republican office seeker from New York, he once lost to a candidate backed by Ronald Reagan." Elsewhere, he asserts, "Greed didn't drive me."

In truth, Deaver reveals most when he probably thinks he's not being revealing at all. This is a fellow who, after all, says he really could have been happy "working as a musician in clubs and lounges." And yet, he was driven by something else:

"My exposure to the Reagans did give me an appreciation for good things, a fine painting, the best piano. One of the great luxuries I allowed myself, after I had launched my own consulting business, was to buy the ultimate in pianos, the Busendorfer, made in Vienna. It was delivered on Christmas Eve of 1985. The cost is not quite twice that of a Steinway.

"A few days later, I encountered William F. Buckley, and confided proudly that I had just gotten a Busendorfer. 'Ah,' he said, in that voice like fur, 'how wonderful for you. I have two of them.' " :: Reid Beddow is an assistant editor of Book World.