The Starless Sea by Erin Morgenstern

From the New York Times bestselling author of The Night Circus, a timeless love story set in a secret underground world—a place of pirates, painters, lovers, liars, and ships that sail upon a starless sea.
Zachary Ezra Rawlins is a graduate student in Vermont when he discovers a mysterious book hidden in the stacks. As he turns the pages, entranced by tales of lovelorn prisoners, key collectors, and nameless acolytes, he reads something strange: a story from his own childhood. Bewildered by this inexplicable book and desperate to make sense of how his own life came to be recorded, Zachary uncovers a series of clues—a bee, a key, and a sword—that lead him to a masquerade party in New York, to a secret club, and through a doorway to an ancient library, hidden far below the surface of the earth. What Zachary finds in this curious place is more than just a buried home for books and their guardians—it is a place of lost cities and seas, lovers...