TALKING AT THE GATES: A Life of James Baldwin by James Campbell (Viking: $21.95; 297 pp.). "The price a Negro writer pays for becoming articulate is to find himself, at length, with nothing to be articulate about." So wrote James Baldwin in 1952, and it's a harsh assessment with which James Campbell, an editor of London's Times Literary Supplement, seems to agree. Campbell, who first met "Jimmy" in 1980 as a star-struck college-magazine editor, is entirely sympathetic toward Baldwin the individual but not Baldwin the writer, at least from the early 1960s onward; he attributes much of the low quality of Baldwin's later work to involvement with the civil-rights movement. This evaluation seems blinkered. How could Baldwin not put political action before literature so long as his homeland was doubly prejudiced against him--for being both black and gay? So long as the FBI could maintain a file on him running 1,750 pages; so long as his agent could tell him to burn the manuscript of "Giovanni's Room" largely for its homosexual content? It's jarring to encounter such a view in a book otherwise vivid and fair-minded.