Charles, the book itself is quite expensive. This site has a version you can print and bind if you want a hard copy.
I started with google maps just plotting points and drawing lines but by the time you get to the 420 clue & the 560 clue the Michelin map was a big help to see where my final zone was. You will need a smaller map in the zone for the 650 clue (assuming you reach the same conclusions I did) can’t help you much on the 520 as I’d be reporting I had the owl if I had this one sussed :-0
you can get historical data and Ariel views through geoportail.fr who host all the IGN info (map providers for France) – it’s like google just far superior.
hope that helps & enjoy. – I have.