"Debbie Ishlon has written a novel."
"Crazy, man. Are you in it?"
The fact, the surprise and the question were ricocheting through the pop-music trade last week. Girl Singer (Doubleday; $3.95 ) was in the bookstores, and although the world in general had never heard of Deborah Ishlon, big-time agents, smalltime clarinetists, deejays, artists-and-repertory men, photographers and music publishers were browsing with interest. They all knew her as a 34-year-old former secretary who became the trade's nimblest pressagent and has lately assumed the portentous title of Coordinator of Creative Services for Columbia...