The Gospel of Sheba by Lyndsay Faye

A librarian is tormented by a lethal volume of black magic

When A. Davenport Lomax's young daughter asks him whether spirits and faeries are real, the Edwardian librarian just pats the little darling on the head. But when a desperate man emerges from the winding passages of the library muttering about demonology, he gets Lomax's attention. Theodore Grange is a member of the Brotherhood of Solomon, a secret society dedicated to unraveling the mysteries of black magic, and he believes he has found a book written by the Queen of Sheba herself. Said to hold the answers to one thousand demonic mysteries, the tome will poison any man who dares read it.

The next time Lomax sees him, Grange is at death's door. To uncover the truth about The Gospel of Sheba , Lomax agrees to accompany Grange to a meeting of the brotherhood, where he will encounter darkness that threatens his life, his family, and his soul.