Amazing. Unlikely as it seems, Bud Abbott and Leu Costello, the burlyque funmen who became the country's two highest-salaried citizens, provide Bob Thomas with a hellbent-for-heartbreak tale that sometimes makes the scalp prickle and the eyes mist over. Perhaps his key asset was the cooperation of Eddie Sherman, the team's long-time manager and friend. Despite vulgar beginnings the boys never used smut, and even in Vegas they kept Sunday-clean with their endless ""Who's on First?"" routines. Both are consistently interesting. Little Lou's heavy-handed dementia for money and power turns the table on Bud the straight man, making him the real-life he-who-gets-slapped. Bud was much more soft-hearted and likable than his flashy con man role would allow, and lovable, bumbling Leu was an iron-willed authoritarian. Both had a vast gambling mania and their eventual tax problems became crippling in the extreme; the IRS looms as a gigantic villain and supplier of much of the book's pathos. Unforgettable moments: Lou giving a great radio performance for an audience of rheumatic children just hours after his infant son's death by drowning; his own death on the last zesty sip of a strawberry soda; and Bud's alcoholic, stroke-filled, epileptic, crawling, joint-by-joint expiration under the IRS steamroller. Strong stuff almost solemnly told.