Very interesting reading, informative, a good planning guide, it's not much use as a tool once you are on the water but it does make interesting reading on your way through the canals.
If you're planning to take a boat onto the French canals as we did, I'd recommend this as one of the books to take, you can bore the crew to death with little tit bits of information.
My advice is to use this book to plan your route and order the Navicarte map books for the canals you then decide to use, they have very detailed maps of all the canals, locks and moorings along the length of canal you're on. The numbers on the canals in this book will match the Navicarte book numbers 1-29, 19 altogether, (don't ask me). Sadly not many of them are available on Amazon UK, they are French with English and German translations of each entry but in less detail. Try searching for Navicarte on Amazon.fr