''Hell, that's different. That's a pop song now, nearly 'bout,'' Sun Records' producer Sam Phillips famously enthused on hearing neophyte Elvis Presley turn the bluegrass waltz ''Blue Moon of Kentucky'' into rock's seminal lightning bolt. But the Pelvis had help from guitarist Scotty Moore and bassist Bill Black (drummer D.J. Fontana later joined the band). In The Blue Moon Boys, the first book to focus on the formative trio, Ken Burke and Dan Griffin sometimes employ fan-club prose and off-color anecdotes, and omit the fact that Black's next band played on the Beatles' 1964 U.S. tour. Still, they offer substantive info about the boys whose rock made Presley roll.