As I said on the French forums, I've read about 70% of the book and even if I already knew a lot of things inside it, I learned a lot others as well. My favorite part is how the entities communicate with the "command" element, that is a part that I always missed in my previous games.
I learned a lot about SFML/OpenGL as well and that is really a good thing.
I'm looking forward to go through the network part, that should be very interesting =)
I've read a lot of books about how to make a video game before. That is the one I prefer. It's clear, there are a lot of examples, if you don't get a part at first read, you get it at second, the examples are linked together and the final (game) goal is well defined. Perhaps my past exeperiences with SFML help me in understanding it, but it doesn't remove the clarity the authors manage to have.
Authors, the more I read the more I love you !