Alchemy by Maureen Duffy

Jade Green's life takes a turn for the bizarre when she accepts a curious legal case--that of a university professor accused of Satanism. As Jade delves into the strange circumstances of his dismissal, she finds herself drawn into a 17th-century manuscript, the original of which has been stolen from the professor's briefcase. It is the diary of Amyntas Boston, a young woman--raised as a boy--awaiting trial for dabbling in witchcraft. As past and present intertwine, Jade feels her life curiously resonating with that of Amyntas.