Once the world flips upside down, this book is clickable on the ceiling to spawn Necretia Widowmaker for the Puzzled quest. It is in the same room as the chest, but the map coordinates change when the flip happens, so the old icons don't line up anymore.
Level 97 ^^^. Spawns in piano room with 4 Vengeful Musicians (lvl 97^^) after the world flips upside down and you click on the book on the ceiling in the room with the chest.
Lvl 98^^^ spawns with Nes'tal Webspinner and A'Damis Venomstinger (both lvl 98^^^) after the world turns upside down and you click on the book on the ceiling in the room with the chest.