Veil of Lies by Jeri Westerson

This first installment in a series has Crispin Guest, as a disgraced knight who was stripped of his rank after a treasonous plot against Richard II. He is forced to live by his wits on the streets of London making his living as a Tracker, the medieval equivalent of today's PI. He takes a job from a reclusive prosperous merchant to spy on his wife and find out if she has been unfaithful. When the merchant turns up dead, Crispin must unravel the mystery. Doing so involves a family dispute, a ruthless mob of Italians, and a religious relic, in this enjoyable 14th century tale of murder and intrigue.

Westerson has created a memorable character in Crispin Guest, who is frustrated by his societal downturn and has to constantly battle those feelings. When in the course of solving this mystery he manages to fall in love with a commoner, he has to come face to face with his own prejudices. This authentically detailed period piece is a real page turner. Westerson has an encyclopedic knowledge of the medieval period and an obvious love for the hard boiled detective genre. Serpent in the Thorns is the next book in the series, and I can't wait to return to the gritty world of 14th century London.