Neal Pollack is dead. And Neal Pollack killed him, but probably just for now. This time, the author's fictional namesake surfaces as a dead rock critic -- or, as his pompous rival-turned-biographer Paul St. Pierre calls him, ''the living, breathing essence of America's music, its dark Baudelaire Rimbaud genius, its Celine, its Brecht.'' Pollack the character has a Zelig-like (or is it Forrest Gump-y?) knack for showing up for great moments in rock -- and a talent for getting kicked in the teeth once they happen. Conduit or parasite, he's a handy delivery system for Pollack the author's brief history of modern music. This lively but mortally attenuated in-joke will likely be lost on all but the most scholarly of music geeks.