The U.S. Air Force's parachute rescue jumpers (PJs for short), though less well known than other elite military groups (like the Navy SEALs or Green Berets), have an equally hazardous mission: rescuing pilots who get shot down behind enemy lines and aiding service personnel in similarly dire circumstances. This crisply written biography of a PJ, Senior Master Sgt. Jack Brehm, offers a look at one squad of parachutists, pilots and combat divers, which numbers about 300 men. Brehm, based on Long Island, coordinated efforts to rescue a helicopter crew of PJs who plunged into the mid-Atlantic while trying to save a fisherman during a 1991 nor'easter. Magazine journalist Nelson devotes a chapter to Brehm's behind-the-scenes role, which got only brief coverage in Sebastian Junger's 1997 bestseller The Perfect Storm. However, fans of Junger's book seeking the same high seas adventure and suspense probably will be disappointed by this workmanlike bio. Though PJs have flown missions over Kosovo and Iraq, participated in the Gulf War and saved the lives of U.S. servicemen in Vietnam, Brehm's exploits, at least as recounted here, are of a more mundane sort, like rescuing seamen in trawlers or a climber on Alaska's Mt. McKinley. Nelson rounds out his canvas with capsule accounts of the deeds of numerous PJs, and each chapter is prefaced with Brehm's first-person testimony, so we get a convincing portrait of a modest hero and family man who gives his life meaning by putting himself at great risk, as the PJs' motto has it, ""that others may live."" Photos not seen by PW. Author tour. (Feb.) FYI: Jack Brehm is scheduled to appear on Good Morning America.