The scenario sounds promising: Walt Diney's metamorphosis from a self-trained, second-rate, bankruptcy-prone cartoonist into the pioneering mastermind of mass entertainment. But Bob Thomas' biographies (Thalberg, Winchell and Selzniek, among others) sit on the brain the way a lifesaver sits on the tongue--sticky-sweet and long-lasting, with a big hole in the middle. Walt Disney is doubly hollow, devoid of either psychological portraiture or artistic evaluations. Instead the biographer serves up a pleasant, plodding what-Wait-did-next account, mercifully punctuated by choice excerpts from the ""story meetings"" that sparked Disney studio projects. More of those excerpts (and less about Walt's sons-in-law or his fondness for chili) might have conjured up the Disney gift for matching music with images or the Disney genius for comedy. Thomas concentrates rather on the Disney bank balances. The writing perks up noticeably when the miles of Disney red ink finally begin to turn very, very black. The strongest chapters celebrate the nativity of Disneyland; the weakest skim lightly over such masterpieces as ""Fantasia"" and ""Bambi."" Controversial items (like Disney's McCarthy-era politics) are skirted, critical contributions (like Richard Schickers The Disney Version) are ignored, and an aura of folksy hagiography creeps in as Disney approaches senior citizenry. Yet his quoted words exude so much vitality that Bob Thomas's pallid but detail-crammed volume may supply some satisfaction. It's more likely; however, to justify its paper consumption by its usefulness to the biographer who someday connects the man with his legacies.