Mohr has written a self-critical as well as vengeful book about being miserable for two years on ”Saturday Night Live” called Gasping for Airtime. Hired as a writer and ”featured performer” during the ”SNL” heyday of Chris Farley, Phil Hartman, and Mike Myers, Mohr complains he never felt accepted or got enough on-camera time. Sometimes, his details about the closed-club atmosphere of the show provoke our sympathy, as do his admissions of excessive drinking and panic attacks. His descriptions of Al Franken, Rob Schneider, and Ellen Cleghorne as jerks and of an excellent fistfight between Norm Macdonald and a staff writer contribute to ”SNL” bad-behavior legend — no small feat. And it takes either a big man or a guy trying to sell books to admit he stole another comedian’s routine out of desperation. His public contrition here is almost convincing.