At 88, historian David Levering Lewis, a biographer of W.E.B. DuBois, has filled in gaps in his knowledge of his own family line, and he takes readers along on the journey.

For most people fortunate enough to have a garage, it’s a place to park a daily driver or two, store the cornhole board between backyard barbecues, and stash the trusty Lawn-Boy, along with some ...