The business of A&R (artists and repertoire) people at a record company is to sign new acts and nurture their careers, and lately no one in the industry has been hotter than Jim Cantone. Now the big time calls, and Jim accepts an offer to become head of A&R at industry giant WorldWide Records, founded and still run by the legendary maverick Wild Bill DeGaul. Little by little, though, it dawns on Jim that he has walked into a vipers' nest, and he must choose between picking up a dagger in a bloody palace coup against DeGaul or standing by him and losing everything.          Never before in fiction has the music business been so thoroughly nailed, but A&R is as much Julius Caesar as it is The Player: for all its great wit and dead-on insider texture, it's as wise about human nature as it is about one very dysfunctional industry.