[With "One Hell of an Actor,"] Mr. Kanin has written a chatty, intentionally gossipy novel (using real names of the famous interspersed with the fictional characters), which somehow fails to take off. Perhaps that is because the Kanin-persona narrator begins his story with a fascination for the life and times of a turn-of-the-century San Francisco actor named John J. Tumulty and a desire to reconstruct the feeling of the man and the era. This is an exciting idea, but it becomes lost in an across-the-years detective story, told in a series of interviews, letters and diaries. The story reveals more about the descendants who inherit the grand-old-man's stubbornly thespian blood than about the man himself or about what it was like to be an actor in his particular time and place. What might have been rich drama trails off into thin sleuthing.