Eric Booth says he has never before encountered the kind of enthusiasm that greets him after performances of "St. Mark's Gospel," and therein lies a problem. Strangers appear in his dressing room and want him to autograph their Bibles.They want to pray with him. They want him to come for Sunday dinner. And they leap to conclusions about his personal religious convictions -- conclusions that happen to be off the mark.

"Have you accepted Jesus personally into your heart?" they ask him.

"When they say that, I know what answer it is they want to hear, which isn't a truthful answer for me," says the 30-year-old actor who, since January, has been trying to fill a demand for "St. Mark's Gospel" beyond what the original star, Alec McCowen, could handle.

"I have to fight like the dickens to avoid having born-again words put in my mouth," says Booth. "I try to be charming and ooze my way out of it. I'll say, 'Jesus as a religious and historical figure has become much more important in my life because of the show . . .'" But some of his visitors detect a note of evasion in that answer and get belligerent.

That's when Booth, who describes himself as an "eclectically Christian New York actor," sends a prearranged signal to his stage manager, who promptly alerts him to an important call from New York. (Even that maneuver doesn't always settle the issue. Several of his visitors have grabbed Booth and tried to make him kneel with them and accept Christ on the spot.)

These are extreme cases, however. "Usually, they say, 'Oh well, we like the play . . . I'm sure just dealing with this material will bring you around before long,'" And Booth says it has, in fact, had an influence. "I haven't become a born-again Christian," he says, "and I haven't really become more religious. But you say those words over and over again and it affects your mind."

Booth auditioned for McCowen and producer Arthur Cantor in March of last year, then spent nine months memorizing and rehearsing by himself, and then a month working with McCowen before his initial engagement in January -- five successful weeks at Chicago's Studebaker Theater. Since then, he has done the she in Birmingham, Ala.; Atlanta, Ga.; Rome, Ga.; Lincoln, Neb.; Columbia, Mo.; Grove City, Pa.; York, Pa.; Greenwich, Conn.; and Midland, Mich., among other cities. Yesterday he opened a two-week engagement at the Kennedy Center's Terrace Theater.

His credentials for the assignment include work on Broadway, on TV and in regional theaters -- and, unavoidably, the fact that he is the great-great-great-grandson of a famous American actor with the same last name. The actor in question, for better or worse, is John Wilkes Booth, rather than Edwin Booth. But none of the family history has loomed very large in Eric Booth's life, he says, because his branch of the family has been out of show business for generations -- since John Wilkes Booth's daughter Ogirita failed to make a career fr herself on the stage. (Perhaps her first name had something to do with it, her great-great-grandson theorizes.)

He was born Eric Booth Miller, the son of a magazine editor and a school administrator. He knew of his theatrical ancestors as a child, but "I didn't take all the Booth stuff very seriously," he says. That was until he appeared in a production of "Under Milkwood" at Middlebury College in Vermont and decided to become an actor, ditching plans to attend Yale Divinity School the next fall. When he joined Actors Equity, he says the union already had an Eric Miller, so reverting to Booth seemed like a natural move. (His wife, also an actress, has a name that raises eyebrows even higher: le Clanche due Rand. But no relation to Sally).

Booth has yet to pay a visit to Ford's Theatre, scene of his great-great-great-grandfather's last bravura performance. But he did appear at the Kennedy Center in 1977, playing an Egyptian slave in "Caesar and Cleopartra," starring Rex Harrison and Elizabeth Ashley. He is not a bit player by nature, he says, so he doesn't remember that experience with fondness. He isn't about to forget one night, however, when he went to a restroom during the performance and, trying to find his way back to the wings, accidentally pushed through a door into one of the Center's main public thoroughfares, and realized the door had locked behind him.

With only minutes left before his next cue, Booth charged up and down the loby searching for a way to get backstage. Dressed only in what he describes as a "gauze diaper," he came face to face with the imposing bronze bust of President Kennedy, and caused a small commotion before a fellow slave finally came searching for him and let him back in the same door through which he had made his initial, Alice-in-Wonderland-like-plunge.

Nothing like that can happen with "St. Mark's Gospel," however. This time, Booth will be appearing fully clothed and, since he is the only member of the cast, he'll be on stage every minute. He prefers that arrangement.