"A Discovery of Witches" is a fantasy novel by Deborah Harkness that follows the story of Diana Bishop, a historian and witch who discovers a mysterious manuscript in the Bodleian Library at Oxford University. This discovery draws her into a world of magic, where she encounters various supernatural beings, including vampires and daemons. As Diana navigates her newfound powers, she forms a complex relationship with Matthew Clairmont, a vampire and geneticist. Together, they seek to uncover the secrets of the manuscript while facing challenges from both the magical and human worlds, ultimately exploring themes of love, identity, and the balance between science and magic.