The book provides you with a nice basic grounding in the history and operation of medieval European crossbows. It is entertaining and not at all stuffy. It is in short a very agreeable lesson in the history of technology. After you've read it, you can impress your friends with your relatively vast knowledge about crossbows. If you see crossbows in a museum, you can make some educated guesses about the bows without even reading the museum's captions (which are sometimes wrong, even at big name museums).