The FFRP guide is very good. I found mine in a bookstore in Geneva.
It is not my favorite route. Quite scenic, but not so historically accurate. The book explains that they wanted a route which is similar in appearance to what the original pilgrims were on, rather than retrace their steps. The local towns have adopted it to some extent, and there are quite a few St. James statues, place names, etc.
In Moissieu sur Dolan there is a fantastic privately owned chateau which takes in pilgrims, not to be missed.
The final portions through the Cote du Rhone, into the Auvergne, and into Le Puy is quite nice.
We did the Rhone section during apple harvest---best apples in the world.
Have fun!