Il castello di Eymerich
Il castello di Eymerich ("Emerych's Castle") is a book written by Valerio Evangelisti, an Italian historian and writer of historical fantasy. In chronological order, it is the seventh book in a best-selling series whose central character is Nicholas Eymerich, an inquisitor of the Spanish inquisition - a historical character, whom Evangelisti adopted to his novels following a detailed research of sources concerning Emerych's figure. It has been translated into many languages, most notably German, French, Spanish and Portuguese. Plot summary 
The plot of the book is divided into three threads:

The main thread 
Takes place in Montiel in Castile, Spain, in 1369, during the civil war between king Peter of Castile and pretender Henry of Trastamara. Peter of Castile is defending Montiel, besieged by the pretender's forces, which consist mostly of mercenaries commanded by a historical figure Bertrand du Guesclin. Inquisitor Nicholas Eymerich is called in to investigate the use of black magic by the besiegers and the use of cabal by the defenders. "The five men from Girona" 
This thread takes place prior to the main one. It depicts a group of Dominicans sent by the Pope to the Castle of Montiel in a mission to use demonology against cabalistic magic . "The Chosen One" 
Takes place during World War II in a concentration camp Dora, where Sturmbannführer SS Viktor von Ingolstadt is conducting an experiment to revive a dead body to support his quasi-scientific research concerning electricity. Characters

Historical and fantastic themes and motifs

Back story

Influences 

2001 Italian novels
Italian fantasy novels
Italian historical novels
Novels set in Spain
Fiction set in the 1360s
14th century in Castile
Novels set in the 14th century