This biography of J.D. Salinger appears just a year after his death at age 91; the biographer, Kenneth Slawenski, worked on it for eight years, while maintaining a website (www.deadcaulfields.com) devoted to the life and works of his subject. His hope is to “deliver a true and fair and unsentimental account of Salinger’s life justly infused with appreciation for his works.’’ A commendable resolve, and Slawenski for the most part fulfills it, especially in his role as appreciator. He has been preceded by other biographers, notably Ian Hamilton, whose attempt was thwarted by legal processes Salinger instituted. The result was an abortive book (“In Search of J.D. Salinger’’) mainly about the search. There have also been memoirs, one by his live-in mate for a year, Joyce Maynard, and one 30 years ago by his daughter, Margaret. But Slawenski fills in a great deal and connects the dots assiduously; it’s unlikely that any future writer will uncover much more about Salinger than he has done.