This fantastically rich novel (1980) from Umberto Eco (http://en.wikipedia.org/wiki/Umberto_Eco) is set in Italy in the Middle Ages.
It is not only a narrative of a murder investigation in a monastery in 1327, but also a chronicle of the 14th century religious wars, a history of monastic orders, and a compendium of heretical movements. A thick slab of education and entertainment rolled into one.
To whet your appetite you may imagine Sean Connery as Franciscan Friar William of Baskerville and Christian Slater as Benedictine Novice Adso of Melk, and then watch the film version of 1986 (http://www.imdb.com/title/tt0091605/?ref_=sr_1).
It is available on DVD at (http://www.amazon.co.uk/The-Name-Rose–Connery/dp/B0001Z65NU/ref=pd_sim_b_5).
The novel runs to 512 pages in the Vintage Classics paperback edition. An excellent read.
ISBN 978-0099466031
Umberto Eco