Elsie Camden was orphaned young. She grew up learning her world's harshest rule: wizards who can afford it buy the power to cast spells, and a rarer few are born able to break them. Elsie is one of the second kind, which makes her a criminal in an alternate Victorian London. For ten years she has broken spells in secret for the Cowls, an underground band fighting the aristocracy.
Her arrangement holds until Bacchus Kelsey, a wealthy young spellmaster fighting for standing among London's magical elite, catches her mid-job. Rather than turn her in, he strikes a bargain: her help with the enchantments on his estate, in trade for his silence. Long hours in close quarters wear down the distance between a criminal spellbreaker and a man with everything to lose by knowing her.
The bargain turns urgent when spellmasters start dying and their spellbooks vanish with them. The killings trace back toward the Cowls, the very group Elsie has served for years without question. She has to work out how much of what she was told about them was ever true. Her loyalty to the cause now has to survive doubting the people who run it.
Spellbreaker is the first book of Holmberg's Spellbreaker Duology. It is a slow-building historical fantasy, one that spends its opening chapters on London's class divide and magic system before closing on a cliffhanger.