An unauthorized biography of talk-show host Johnny Carson that could as well have been authorized--Carson should hardly object to a fact in it. As sympathetic as a Tonight Show camera, Carson is like a long dip into a warmed pool. Johnny himself is fairly discreet about his life and $$-ed life-style, and has told his friends to be the same way. So Corkery squeezes some fresh juice into his tale by having interviewed Carson's first three wives (Joan, Joanne, and Joanna). Unfortunately, these interviews get recycled throughout the text, with each requoting of the same material de-energizing the page being read. Carson's story is just what it has always appeared to be: nearly all on the surface. Seemingly, he has few skeletons in the closet, though Joanna alludes to his sleeping around in the later, Beverly-Hills years of their marriage (""Well, that goes with the territory. . .All the women that I respect who have gone through similar experiences tend to feel you should look away, and if the family is strong and basically unfragmented, it will hold together""). In the end, however, she traded Johnny for one of the great divorce settlements of the century. (Mamie Van Doren's kiss-and-tell autobiography, Playing the Field--reviewed below--gives a blow-by-blow account of her bedtime frolics with Johnny.) Carson's fourth marriage, to Alexandra Maas, includes a prenuptial agreement. An obsessive magician and showman since childhood, Carson's foremost daily interest upon rising is his evening monologue, which must be plucked fresh from the day's events; and over his past 25-year tenure as host of The Tonight Show, this obsession has eaten up his ""family time."" Charming as he is, he's much like a shy, Midwestern Edgar Bergen and worldly-wise Charlie McCarthy rolled into one, seamlessly joined entertainer-dummy. Bland but well-written, aside from the recycling.