In post-WWI England, former Royal Air Force pilot Hugh Anthony Disward inherits his late grandfather's mansion and, with it, custodianship of Dantalian's Bookshelf, an archive holding 900,666 forbidden Phantom Books. Its guardian is Dalian, the young 'Black Biblioprincess' who can unlock the books' power, and together they investigate incidents where lost tomes wreak havoc on ordinary people. This manga adapts the original light novel series.