Believe me, there are a lot of us waiting for said books. *Albatros Pubs - the makers of Windsock and the Datafile series - has had a Breguet 14 Datafile Special planned for quite some time, with no release date in sight, unfortunately.
For the Caudrons wait a year - Albatros has announced a Datafile each for the G.3 and G.4.
For the Salmson you're in luck - track down the new Flying Machines Press (FMP) book on the type. *Highly recommended.
For overall French machines, try to find the FMP tome on French Aircraft of WW1. *Anything you would want to know about French aircraft is in this book. *Now I have heard that some of the info is not accurate - plus some of the drawings and color profiles are suspect - but it's the
only book that looks at French WW1 aircraft in general, and anyone who whines about it better be prepared to show something that has come out that's better.
If you're into modeling, then check out my web pages:
http://www.wwi-models.org/misc/FrenchWW1/index.html