There is a book on the reptiles of Turkey, in Turkish. I have a German field guide to snakes of Europe which covers all the way south through the middle east and over the Caucausus to the Caspian sea. Should cover all of Turkey. Anderson and Leviton's Reptiles of the Middle East (and SSAR reprint) will have some species as well. Latafi's Snakes of Iran (also through SSAR) may help as well.