“That’s a big boy’s book,” Mr. Walzer said.

Expensive rare books sell well here, Mr. Walzer explained, partly because the island has become a popular destination for “people who have way too much money,” but also because honeymooners and other visitors often want to take home something more meaningful and less common than a diamond bracelet, say. Books offer tourists “something tangible and not digital,” he added; they’re not just another posed photo in front of the sunset.

Right on cue a customer interrupted to ask whether pictures were allowed in the store: “It’s so cool.”

“Sure,” Mr. Walzer said.

Almost despite itself, the shop has become a tourist attraction. That is especially strange for Mr. Walzer, who for years called the cozy place home. He alternated beds. One is hidden behind shelves now displaying copies of Homer’s “Odyssey” and the Harry Potter series in ancient Greek. The other one (“the master bedroom,” Mr. Walzer called it) sits above the German section. That spot is now occupied by one of the store’s employees, Katie Berry, a 22-year-old graduate in English from Harvard (“Surprise,” she deadpanned) who was spending her third summer sleeping amid the stacks.