In The Lost, Daniel Mendelsohn recounts his search for the circumstances of the deaths of his great uncle Shmiel and five other members of his Jewish Ukrainian family. The book is many things: a family history, a meditation on Jewishness (with frustratingly academic looks at biblical texts), and a detective story, as Mendelsohn travels from Ukraine to Australia to Israel to Denmark in search of elderly Jews who might be able to fill him in on the details of his kin's final living months. The Lost is at times moving, though the emotion is frequently undercut by the author's meandering digressions and winding sentences (one particularly egregious example is 179 words long), on the whole similar to the way Mendelsohn's grandfather would tell stories, ''all that background, all those Chinese boxes; and then, suddenly, the swift and expert slide into the finale.''