Sister Pelagia and the Black Monk — Boris Akunin

In the middle of the night, a disheveled and badly frightened monk arrives at the doorstep of Bishop Mitrofanii of Zavolzhsk, crying: “Something's wrong at the Hermitage!” The Hermitage is the centuries-old island monastery of New Ararat, known for its tradition of severely penitent monks, isolated environs, and a mental institution founded by a millionaire in self-imposed exile. Hearing the monk's eerie message, Mitrofanii's befuddled but sharp-witted ward Sister Pelagia begs to visit New Ararat and uncover the mystery. Traditions prevail -- no women are allowed -- and the bishop sends other wards to test their fates against the Black Monk that haunts the once serene locale. But as the Black Monk claims more victims -- including Mitrofanii's envoys -- Pelagia goes undercover to see exactly what person, or what spirit, is at the bottom of it all.

Fans of Sister Pelagia and the White Bulldog, the first book in Akunin's Pelagia trilogy, will be instantly mesmerized -- and frightened -- by this latest foray into Zavolzhsk's spiritual underworld.