"Kean" is a curiosity -- a play by Jean-Paul Sartre based on a play by Alexandre Dumas (pere) based on the exploits of Edmund Kean, the 19th-century actor and rake.

Sartre wrote his version in 1955, but the production that opened last night at Arena Stage is said to be an American premiere. If so, it is a premiere that goes a long way toward explaining its own belatedness. Both the play and the three-hour production have their slack periods, when Sartre is playing obscure games with theatrical conventions from Dumas and elsewhere, and when the action brings several truly deplorable supporting performances to stage center. You can't help wondering at these times if Arena hasn't spread its people too thin, what with the three-play repertory running simultaneously in the Kreeger these days.

But "Kean" provides a meaty role for one exceptional actor, and Arena has provided him. Stanley Anderson in the title role gives a hugely appealing performance that is almost grounds enough for seeing this play -- or for producing it. Whether on stage playing Othello with a hangover (and an incompetent Desdemona), or in Kean's dressing room juggling visits from women and rival suitors, or in the fashionable salons of London Society scandalizing his hosts, Anderson is a delight.

Edmund Kean startled the London of his day with his noble and horrifying portrayals of Othello, Shylock, Richard III and Lear. "To see him act is like reading Shakespeare by flashes of lightning," said Samuel Taylor Coleridge. He also lived up to his contemporaries' worst prejudices against men of the theater. He drank, he fell into debt and he chased women high and low.And Sartre, as you might expect, was fascinated by the relationship between Kean's professional and nonprofessional lives, wondering which was real and which was sham and where the twain would meet.

"I sometimes wonder if true feelings are not simply bad acting," Sartre has Kean say -- and there are many more variations on that theme.

In keeping with the comic flavor, the period acting in "Kean" is caricatured, but Anderson presents a far more plausible and respectful picture of 19th-century histrionics than Lilli Palmer and Co. managed in the recent "Sarah in America." He cuts quite a sympathetic figure, in fact, standing before his dressing-room mirror, addressing himself as a "great plowhorse" and telling himself to "go and plow through your Shakespeare."

The plot is largely concerned with an amorous competition between Kean and his crony the Prince of Wales for the favors of a Danish diplomat's wife. Kean himself, meanwhile, is being pursued by a young heiress, who is being pursued by a nobleman, a fellow Kean describes as "descended in line direct from the Plantagenets -- you might almost say he slid down."

Kean seems bent on strangling himself in his own entanglements. "How complicated things are getting," he observes at one point. "And I love complications."

Set designer Marjorie Kellogg has installed all this complexity on a complex interlocking assembly of wooden platforms. During the "Othello" scenes of the second act, massive box seats roll in through the walkways to accommodate the Prince of Wales and other noteworthy members of Kean's audience. Nan Cibula's impressive costumes include one for Kean's Othello that is a dead ringer for the original Kean's actual costume in the role, as preserved in a contemporary illustration included in the playbill.

Among the minor roles, there are some sorry pieces of miscasting, resulting in questionable accents, forced comedy and evident anarchy. But Richard Bauer as the gay Prince of Wales, Annalee Jefferies as the rambunctious Anna Danby, Robert W. Westenberg as her suitor and Mark Hammer as Kean's manager give Anderson substantial support.

KEAN by Jean-Paul Sartre (English version by Frank Hauser), based on the play by Alexandre Dumas; directed by Martin Fried; settings by Marjorie Kellogg; lighting by Hugh Lester; with Stanley Anderson, Richard Bauer, Annalee Jefferies, Halo Wines, Joe Palmieri, Mark Hammer, John Neville-Andrews and Robert W. Westenberg.

At Arena Stage through April 26.