Louis Sachar, a prolific author of children’s fiction, is best known for “Holes,” which won both the National Book Award and the Newbery Award in the late 1990s. “Holes” is a witty, slightly postmodern tale and its treatment of social (in)justice quickly earned it a reputation as a children’s book with breakthrough adult overtones, and it has remained a classic for a quarter century. Its earliest readers were also the earliest readers of Harry Potter—and now that they are pushing 40, Sachar has written them an adult novel with a nostalgic glance at the wizards of their childhoods.