The Fragile Threads of Power is the first book in a high fantasy series by V. E. Schwab. It follows the Shades of Magic trilogy: A Darker Shade of Magic, A Gathering of Shadows, and A Conjuring of Light. The Shades of Magic novels take place in a universe where magic is real, and there are four worlds, connected by the cities of London. Red London is pulsing with magic, Grey London is an analog of Georgian London and has no magic, White London is starving for magic, and Black London is corrupted and burnt out.

The series follows the adventures of Kell Maresh, who is a powerful magician called an Antari. The Antari are the only ones able to travel between worlds. Kell is the adopted son of the rulers of Red London and works for the crown as a messenger. In Grey London, he meets a thief named Delilah “Lila” Bard, who dreams of more than her bitter existence on the streets. When Kell smuggles an artifact from Black London into his world, he starts a collision course with Lila and with Holland Vosijk, an Antari living in White London. Holland serves the corrupt and power-hungry rulers of London, the Dane twins.