Saul Bellow didn’t like the word “task” as applied to literature: “tasks are for people who work in offices,” he once cracked. Yet Ruth R. Wisse’s survey in Mosaic of Bellow’s achievement as an American Jewish novelist, “What Saul Bellow Saw,” shows that synthesizing those two parts of his identity, the American and the Jewish, was indeed a lifelong task, one that occupied his fiction from The Victim (1947) to Ravelstein (2000).