Kindness of Strangers : THE LIFE OF TENNESSEE WILLIAMS by Donald Spoto (Little, Brown: $19.95; 409 pp.) : TENNESSEE: CRY OF THE HEART by Dotson Rader (Doubleday: $16.95; 348 pp.)

Two books about Tennessee Williams have just come out, one solid, one sleazy. The latter--which the reader will naturally want to hear about first--is a peephole memoir of Williams’ last, worst years, by the New York writer Dotson Rader.

When Williams met Rader in 1969 the playwright mistook him for a male hustler. This pretty much set the tone of their relationship. Rader denies that they ever had sex. But they did cruise the backroom bars together, getting stoned and sharing the occasional young stranger. Rader provides a vivid account of each expedition, with supplementary scenes of, for instance, Jim Morrison exposing himself at an East Village party.

Lest this sound sensationalistic, Rader also makes it clear what a faithful friend he was to Williams, forever flying off to this or that strange city to pull him out of a tailspin. A typical memory: Williams slumped on the toilet, hair dye running down his face and tears in his eyes. “Get me a priest, baby. I want to die.”

Well, Rader told his friend he was drinking too much. But then he was drinking too much himself, so how much could he say? Rader’s book makes it quite obvious that one of Williams’ biggest problems in his later years was precisely such comrades as himself. With friends like this, who needs strangers?

Skip this creepy book, and turn to Spoto’s biography, possibly the best of an American playwright since Louis Sheaffer’s two-volume study of O’Neill.

The first virtue of “The Kindness of Strangers” is that it provides the most accurate account of Williams’ footloose life in print. (That includes Williams’ loopy “Memoirs,” on which Rader has drawn to pad out his memoir.) Spoto’s research suggests, for instance, that Williams’ famous job at his father’s shoe company may have been a part-time one, not quite so purgatorial as the playwright remembered it.

Spoto has also taken the trouble to interview everyone with the remotest connection to the playwright, from his brother Dakin to the clerk who threw Williams out of a San Francisco hotel in the 1970s for making a row in the lobby. Many of the larger figures in Williams’ life are beyond interview by now, of course, but Spoto has found witnesses to every stage of Williams’ life, and the feeling is that of a full portrait.

It’s the portrait of a man in such precarious balance that it’s a wonder he kept a coherent personality as long as he did. (Clearly the habit of writing helped, and all witnesses agree that Williams was at it every morning, however zonked.)

Everyone is a compound of his parents--but not at full strength. Williams talked as if he literally harbored the spirits of his high-flown mother and his carousing father--who hated each other like poison. Beyond that, he had a living ghost to contend with: his sister, Rose, lobotomized back into a child in her 20s. (She was the one permanent emotional attachment of his life, and the witnesses are again agreed that Williams never failed her.)

A writer with such vivid inner voices would naturally be attracted by the theater. Spoto reminds us that almost all of Williams’ plays reflect his private stock company, even to the late “Clothes For a Summer Hotel,” which supposedly concerns F. Scott Fitzgerald and his wife, Zelda. Narrow your eyes and it’s Williams visiting Rose in the asylum.

“Clothes for Summer Hotel” was a dreadful flop, crushing Williams’ last hope for a Broadway comeback. In this regard, as in every other, he was a divided man, affecting to scorn Broadway success but deeply depressed when it slipped away from him in the 1960s. That began Williams’ “stoned decade,” which Spoto makes clear never really ended--he wrote on pills and alcohol until the end of his life.

One is tempted to see him as a writer destroyed by the Broadway system, but that is not the case. Spoto shows that as a young writer Williams did receive much kindness from strangers representative of that system--notably the agent Audrey Wood, who became a kind of surrogate mother to him in the early 1940s and who never gave up on him until Williams dispensed with her services in the 1960s.

Another bulwark was Frank Merlo, Williams’ lover and major- domo--until, again, Williams began to feel fettered by the relationship. Merlo’s death--again in the 1960s--seemed to remove Williams from a sense of true north, just at a time when he might have been ready to try a quieter and deeper kind of play.

Instead the decline began, the plays getting thinner (with the occasional return to form: Spoto thinks particularly well of the late “Something Cloudy, Something Clear”) and the wanderlust turning into a kind of emotional vagrancy, with disturbing flashes of paranoia. For example, a New York Times editor, Arthur Gelb, had written a biography of O’Neill. That explained why the New York Times was out to get Tennessee Williams.

A sad story, which Spoto tells gently and justly, reminding us that even at the end Williams retained his professionalism as a theater worker and his courtesy as a human being. If he relied on “frequent excursions to the frontiers of illness, madness,” to produce his work, he paid the price of the excursion--and we have the plays.