Blessings in Disguise by Alec Guinness (Knopf: $17.95, 238 pp., illustrated)

It always seems an uneven and possibly unfair distribution of assets when a very good actor is also a very good writer. Alec Guinness has few equals among English-speaking actors, and now in his resolutely self-effacing memoir, he is discovered to be an uncommonly felicitous prose stylist as well.

From his performances, you might well, and correctly, predict that Guinness is modest and guarded to a fault. Just as the real Alec Guinness can only be glimpsed, or speculated upon, behind the several Gascoynes of “Kind Hearts and Coronets,” or the man in the white suit or the schemer of the Lavender Hill mob or the lady-killers, the real Guinness also finds a surprising degree of concealment even behind the narrow letter I.

Now portraying himself, Guinness prefers more often than not to be witness rather than protagonist, electing to be a chronicler of the lives of those he has known and loved--loved, in some instances, with a heroic tolerance for eccentricity.

As Guinness arrived for dinner one evening, Ralph Richardson slugged him for no cause except that Richardson was evidently displeased with the world at large at that moment. After a somewhat offhand apology, the evening went forward.

Befitting the actor who has starred in so many dramas, Guinness thinks dramatically (not melodramatically), delivering life in scenes and settings that are atmospheric and wonderfully shaped, the moments recaptured with fine fidelity, the lives seen in full, in their balanced glooms and glories.

He is the entertainer rather than the tell-all who will at last reveal the scarlet sins and dubious conquests of a distant and discreetly unidentifiable day. Guinness the actor is hard on himself, complaining, for example, of his “pale, ersatz Gielgudry” in an early attempt at “Hamlet.” He quotes Dr. Johnson: “Almost all absurdity of conduct arises from the imitation of those we cannot resemble.” Had he heeded the thought, Guinness says, he “might have been spared many theatrical blunders in later life.”

The reader will have had to know of Guinness’ triumphs; Guinness hardly lets on that there were any. He makes the knighthood seem a reward, not for the years at the peak of his profession, but as a kind of thank you for having defused some anti-British sentiments during a film festival in Mexico City.

His portraits of friends and colleagues--Martita Hunt, Tyrone Guthrie, Sybil Thorndike, Fay Compton, Edith Evans, Ernest Milton, Richardson--are often very affecting, because life was not kind to them equally, although even those who knew the worst of fortune kept their arrogance topped up with infusions of undeterred theatrical ego.

Yet inevitably, Guinness is most interesting and touching when he is closest to his own feelings. He speaks wryly of actors who insist they don’t know who they really are. He was illegitimate, registered as Alec Guinness de Cuffe--Cuffe having been his mother’s maiden name. The father’s name was left blank.

He was, he says, “born to confusion and totally immersed in it for several years, owning three different names until the age of fourteen and living in about thirty different hotels, lodgings and flats, each of which was hailed as ‘home’ until such time as my mother and I flitted, leaving behind, like a paper-chase, a wake of unpaid bills.” (This is, not least, a fair sampling of Guinness’ graceful style.)

At one of the flats, a rather addled, old, spooky former dancer-actress lived on the first floor. The child Guinness, often left alone while Mama went gallivanting, sought refuge with the old woman one terrifying night when he became convinced the house was haunted. So began a brief, bizarre, lovely friendship that Guinness recalls with a characteristic restraint that lets the poignancy declare itself.

His first theatrical crush was on a music hall performer named Nellie Wallace, who wore high button shoes he found magical. He sent her flowers with his ice cream money (he must have been about 7) and had a note from her. In later life, he finds himself remembering the shoes and hoping “they are well cared for in some eccentric museum and, when darkness falls, that they shed their primness, take up idiotic positions and tap out some old, raucous, ribald music-hall song.”

His persisting hero is John Gielgud: “Gielgud and Guthrie did more to liberate the English theater than any others; and John in particular paved the way for what is best in London today. He introduced new directors and designers from home and abroad, encouraged unknown actors, and always cast around himself the finest established performers he could lay hands on.”

Guinness spent two and a half years on active duty in the Royal Navy during the war, with adventures that ranged from the farcical to the perilously heroic. His anger at certain military stupidities is perhaps the strongest emotion in the book.

He has never learned with absolute certainty who his natural father was, although it was most likely a man named Andrew Geddes. Geddes may have persuaded a friend, one of the brewery Guinnesses, to lend his name to the birth certificate. That sort of thing was done then, Guinness says.

Long and happily married and himself a father, Guinness says the question has ceased to stir him. Yet it is clear that the fact he was never claimed hurt for years. Geddes came to call, not long before he died, and gave the boy a half-crown. But it remained for Guinness to take his first wages from “The Cocktail Party” and buy himself the gold watch he had always dreamed his father would leave him. He inscribed it with his favorite line from Shakespeare, “The readiness is all.”

A convert to Catholicism and something of a mystic, Guinness has come at last to a serenity that lends “Blessings in Disguise” a particular and appealing warmth. If he discloses no deep secrets of the actor’s art, he demonstrates what an enchanting and illuminating virtue modesty can be, when it is worn so well.