Possession and Prejudice by Catherine Bilson

How far would you go to save yourself?

Anne de Bourgh is dying, her body weak, ruined by her father’s and her own alchemical experiments. She has just one chance to save herself and get everything she ever wanted.
All she has to do is steal someone else’s life.
Elizabeth Bennet doesn’t know how lucky she is. She’s strong, beautiful, clever… and oblivious to the fact that Fitzwilliam Darcy is hopelessly in love with her.
Such a waste.
Or it would be, if Anne didn’t have a plan.
What would you do if someone stole your life?

Elizabeth Bennet wakes in a strange bed unable to breathe. Her body won’t obey. Her reflection shows another woman’s dying face. Anne de Bourgh has used forbidden alchemy to switch their bodies, and she’s already using Elizabeth’s stolen form to claim everything Elizabeth never knew she wanted.

When Darcy proposes, Anne says yes and demands they marry immediately.
Now Elizabeth is trapped in Anne’s failing body, kept sedated and guarded, while Anne plans a wedding that’s only days away. Once Anne marries and leaves for Pemberley as Mrs. Darcy, she’ll be forever beyond Elizabeth’s reach, and Elizabeth will be left at Rosings to die.

Elizabeth contacts her sister Jane, the only person who will believe the impossible. Together, they race to brew a reversal potion. But Anne has been planning this theft for years. She has Mrs. Jenkinson keeping Elizabeth drugged and guarded. She knows Elizabeth will never obtain the rare, expensive ingredients needed for reversal. She has Darcy’s love, or at least, she has him loving Elizabeth’s stolen face.

Elizabeth has only days, one sister, and a body that’s failing with every breath.
But she’s still Elizabeth Bennet. And she’s never surrendered in her life.
Two women. One life. And only days to determine who gets to keep it.

A spellbinding Pride and Prejudice variation about desperation and identity. What makes you yourself when everything that defines you can be stolen?