Emerging from the shadows of the Great Recession, Clay Jannon stumbles into a job at Mr. Penumbra's 24-Hour Bookstore, a seemingly mundane locale in San Francisco. Yet, as Clay acclimates to the night shift, the store reveals itself as a facade for something far more mysterious. The rare visitors don't purchase books; they 'check out' obscure tomes, fueling Clay's suspicion that this peculiar place is a nexus for something grander. With the help of his eclectic friends, Clay delves into a labyrinthine puzzle, analyzing patterns and decoding secrets that lead them into a conspiracy that spans beyond the bookshop's confines. Robin Sloan spins a tale of adventure and enigma, where a modest bookstore transforms into the heart of a literary enigma, challenging Clay—and the reader—to unwrap layers of history and fantasy.