I'm reading this book very slowly (a couple pages here and there), and I'm nearing the end. It's only 107 pages, and the first third is the introduction. The intro was quite informative, setting the scene of when and where this was written, and the state of France at the time.
The book was written by Charny to help invigorate a new generation of knights and men-at-arms in an age when France was getting its ass handed to it by the English. The Hundred Years War was underway. Charny spends an enormous amount of time describing what is worthy of praise and honor, and what isn't. He compares knighthood to priesthood, and makes it clear that he doesn't like people falling into fashion trends, and being distracted by luxuries when there's important work to be done. He goes so far as to complain about those who wear clothes so close-fitting and short that one can't sit down without showing one's "shame" in the front or the rear.
He complains about those who would rest on their laurels, earn themselves a big gut, and then try to hide it by wearing tight-breastplates that no longer allow them to breath or sit down.
At a time when the clergy felt that a knight should be chaste, he instead says that the love of a woman can inspire men to great deeds, so he basically says to love the ladies, but be discreet. No boasting or bragging.
It's a very interesting read, to see his thoughts on how one should conduct oneself in a life of arms.