We recently had a prolonged discussion on the site of the Philidor Counter-Gambit (start
here and work your way backward), but that's just a (disreputable?) sideline in an opening that can count stars like Azmaiparashvili, Bacrot and Nisipeanu among its adherents. A new, excellent book on the great Frenchman's contribution is GM Christian Bauer's
The Philidor Files, and you can read my review
here. (Originally published in
Chess Today.)