Hugh Anthony Disward, a former Royal Air Force pilot known as Huey, returns to England after his grandfather's death to claim a mansion he never knew existed. Its cellar holds Dantalian's Bookshelf, a library of 900,666 Phantom Books guarded by Dalian, a girl bound to the collection as its "Black Biblioprincess." As Huey becomes her Keykeeper, the two travel the countryside chasing down individual Phantom Books before rogue readers can misuse them. The original light novel series tells each case as a self-contained story.