A dual bio about two of sports' biggest blowhards Muhammad Ali and Howard Cosell might have KO'ed best-seller lists as an oral history. Veteran sports scribe Dave Kindred instead delivers a ringside history of how these two egos came to rule their respective games. Nasal know-it-all broadcaster Cosell was the Simon Cowell of his day, widely reviled but also must-see TV. Ali was a heavyweight champ, militant Muslim, war resister, street poet, and civil rights icon all in one. Kindred believes that through their televised repartee, each amplified the other's fame while representing and hastening the nation's growing cultural pluralism. Yet for all their shared bluster on screen, the two had virtually no relationship off it, undercutting Kindred's attempts to posit larger themes. (An Ali associate even asks Kindred, ''What's Cosell doing in your book?'') Still, he at least produces two solid biographies for the price of one in Sound and Fury.