To see A Life in the Theatre is to revel in David Mamet’s love of actors.

The revival of Mamet’s 1977 play -- which runs at the Gerald Schoenfeld Theatre through Nov. 28 -- follows a veteran actor, Robert (Patrick Stewart), and a novice, John (T.R. Knight), in a repertory theater through various productions over an undetermined period of time. In over 26 scenes and numerous costume changes, their relationship evolves with hilarity and drama.

It is a warmer Mamet play than, say, Glengarry Glen Ross or Speed-the-Plow -- actually, than pretty much most of his signature edgy works.

“It’s got a lot of heart-- dare I say, a certain amount of sentiment?” says Neil Pepe, the show’s director. “It’s a side of Mamet you don’t often see, but to me, what’s lovely is it shows how deeply he feels about this profession. It’s something he’s imparted to me; to treat the theater with respect and know it’s a legitimate career to devote oneself to.”

Structure-wise, A Life in the Theatre gives its actors and directors a unique labyrinth to navigate, with some scenes only a few lines long and others going on for several minutes. Mamet, once an actor himself, wrote them over several months, basing them on “anecdotes, or composites of anecdotes or observations,” he wrote in The New York Times before the play opened in 1977.

With his plummy English accent and classical training background (he’s acted in Royal Shakespeare Company productions since 1966), Stewart is a perfect fit for the role of Robert, imbuing him with wit, pomposity and the anxiety of one who knows his best days on the stage are past.

Stewart -- best known for playing Capt. Jean-Luc Picard in the Star Trek: The Next Generation TV series and its four film sequels, as well as for his role as Professor Charles Xavier in the X-Men movies -- portrayed Robert in a West End production of A Life in the Theatre five years ago. He wrote Mamet asking to be considered for a future Broadway production.

“He loved doing it so much that he didn’t want to stop doing it,” Pepe says. “He had a radically different experience in London; he felt it wasn’t as comedic as it is now.”

T.R. Knight (Grey's Anatomy) brings a subtle style to John, slowly changing from the rookie absorbing an older master’s lessons during their often-terse backstage conversations while gaining the confidence to be himself and risk offending Robert. And the chemistry between the two actors is flawless, adding to the overall appeal of their characters’ interactions.

“Robert has a lot to say about a lot of things, and some make more sense than others,” notes Pepe. “A lot of what he says, despite how he says it, is profound, but it can seem self-serving.”

As the actors apply makeup for a scene, Robert offers John vague advice -- “an aesthetic consideration” -- about how to play the scene.

“Could you...perhaps...do less,” Robert says.

“Do less,” John says incredulously, then asks, “Do less what???”

“You know,” Robert says.

Most of the scenes are set backstage: in a dance room, at a makeup table, in the wings before going onstage, while those that depict stage performances are rife with gloriously comic foul-ups (watch for the expertly executed zipper bit) and blown lines.

“In Mamet’s play, mishaps are not planned,” says Pepe, who’s directed half-a-dozen of the playwright’s works and is the artistic director of the Atlantic Theatre Company, a group co-founded by Mamet and William H. Macy. “The actor is giving his all and it goes wrong and you deal with it. It’s something I love about actors with a certain amount of experience -- their ability to deal with things and find solutions.”

Stewart recently told The Los Angeles Times that “everything that happens in this play has either happened to me in my career or I’ve watched it happen to someone else.”

One expects Knight will be making a similar observation in 20 years or so...possibly when he’s playing Robert.

A Life in the Theatre is playing at the Schoenfeld Theatre, 236 W. 45th St. For tickets, call 212-239-6200 or click here.