The Forbidden Ledger follows Dorian Ash, a nineteen-year-old student at the Hollowmere Institute who discovers that he has only 183 days left to live after being diagnosed with a fatal magical condition known as aether-bleed. With his future suddenly erased, Dorian breaks into the Institute's forbidden library and discovers an ancient supernatural ledger that offers him a chance at survival.

The price is a contract.

The Ledger promises to sustain Dorian's life through magical bonds with powerful users of high magic, granting him a portion of their abilities while permanently changing him with every bond. His first assigned candidate is Vivienne Crowe, the feared and extraordinarily powerful Arch-Duchess of the Ninth Circle, whose affinity is winter.

But forbidden magical contracts carry devastating consequences. If discovered, both parties could lose their magic forever. As Dorian struggles to convince Vivienne to accept the bond, he begins to realize that the Ledger may be offering him more than a second chance at life. Its contracts have rules, its power has a price, and the reason Dorian was chosen may be far darker than he imagined.

With only six months to survive, Dorian must decide how much of himself he is willing to sacrifice for another chance at life—and whether the person he is becoming is worth saving.