"Norton- Toute L'Histoire" by Didier Ganneau was published in 1987, so contains some material on Rotaries, but its forte is early models, pre-Commando.
Due to my little English and less French I can but make vague comments on the text; some of the popular mistakes are not made in the book, and the author seems to know or have researched his Nortons.
The pictures come from a lot of sources, and include a colour picture selection in the middle of the book that contains mainly shots of National Motorcycle Museum and the sammy Miller Museum exhibits.
If you are a Norton bibliophile, or you must have a book on Norton in French rather than another language, it is not a bad buy. If you have good books on Norton already, this book is not a must have.