A discovery of witches / Deborah Harkness.

Deep in the stacks of Oxford's Bodleian Library, young scholar Diana Bishop unwittingly calls up a bewitched alchemical manuscript in the course of her research. Descended from an old and distinguished line of witches, Diana wants nothing to do with sorcery; so after a furtive glance and a few notes, she banishes the book to the stacks. But her discovery sets a fantastical underworld stirring, and a horde of daemons, witches, and vampires soon descends upon the library. Diana has stumbled upon a coveted treasure lost for centuries and she is the only creature who can break its spell.