The Demon's Parchment by Jeri Westerson

This is book three in Jeri Westerson's medieval noir series.   Westerson's main character is Crispin Guest, a sort of medieval Sam Spade, who lives in the Shambles area of 14th century London and uses his intelligence and keen eye for detail as the "Tracker".  He is approached by a Jewish physician, Jacob of Provencal, who wants him to find stolen parchments which someone might have used to bring forth a demon.  These same parchments might be behind a series of grusome murders of young boys.  With the help of his apprentice, Jack Tucker, Crispin must unravel all the mysteries and try to stop the murders.

It is a wild notion to write about a medieval serial killer who murders and defiles children, but in fact this novel is based on a retelling of a very real and strange tale of a 15th century serial killer, Gilles de Rais.  There is even another character in the book who is based on a real person, but I won't give away the surprise by telling you who here.  Just read the book and be surprised and delighted.

Westerson is a skillfull writer who knows her subject.  She has an uncanny knack for making you feel like you are right there in 14th century London experiencing these things along with Crispin.  She has a great eye for historical detail, and her writing is superb.

"Troubled Bones", the latest installment in this series comes out in October.  In the meantime, go here and check out Crispin Guest's Journal, or here and check out Jeri Westerson's webpage.