Under the guise of a detective novel, Lethem has written a more piercing tale of investigation, one revealing how the mind drives on its own "wheels within wheels." Unlike the stock detective novel it shadows, the thriller in which clarity emerges on the final page, ''Motherless Brooklyn'' immerses us in the mind's dense thicket, a place where words split and twine in an ever-deepening tangle.

''Motherless Brooklyn'' has a few problems—including some cartoonlike stock characters and one scene near the end that flirts with maudlin sentimentality—but it works far better than the average hip postmodern novel in terms of sheer emotional impact. Because Lethem never lets the metaphorical and linguistic possibilities of his narrator's illness overshadow his immensely appealing humanity, we really care about Lionel and his search for his mentor's killer.