I love this. I’ve always really liked flags. I also didn’t realize how much more frequently the US flag’s been changed compared to pretty much every other flag. Freaking states.
I have a book on flags and flag families, but it’s pretty old. I used it for a speech class presentation in high school.
Edit: here it is! Copyright 2002. If you’re at all into flags, I’d recommend this book (an updated version, haha). It’s got a really nice layout and covers way more than just country flags.