A 400-page biography of Saturday Night Live and National Lampoon writer Michael O'Donoghue might seem about as essential as a five-hour documentary on the life and work of A. Whitney Brown. But humorist and critic Dennis Perrin's new biography of the writer, who died in 1994, makes an intermittently convincing argument to the contrary. In Mr. Mike, Perrin portrays O'Donoghue not just as a talented, erratic writer, but as an overlooked comic genius who forever changed the face of comedy, investing it with a vicious, slashing integrity while making the world safe for jokes about genocide, dead children, and any number of societal ills. O'Donoghue's career followed a path that reflected the sweeping changes in the times: Beginning as a bohemian playwright and actor in the early '60s, he spent the end of that decade writing the cult comic Phoebe Zeit-Geist. He then moved on to the '70s comedic institutions National Lampoon and Saturday Night Live before spending a seemingly fruitless final decade and a half as a struggling screenwriter who tried to sell out, but found few takers. While Perrin gives an impressively comprehensive account of O'Donoghue's upbringing and early career as a struggling artist, he mostly focuses on the period following his meteoric rise. Perrin's coverage of O'Donoghue's peak period between 1965 and the late '70s borders on obsessive; it seems like half the book is devoted to summarizing every Phoebe Zeit-Geist comic. Unfortunately, while Perrin conveys O'Donoghue's egotism and vicious temper, he never really separates the private O'Donoghue from the carefully crafted image he presented to the public. Large portions of his subject's private life are skipped or mentioned only in passing, and while Perrin excels at illustrating his artistic importance, Mr. Mike still feels incomplete. He might have captured O'Donoghue the artist, but he never captures O'Donoghue the man.