Don't overthink it. Your W gave you the book, asked you to read it, and then initiated a discussion on it. It's hard to look back at a failed marriage and see why/where it fell apart; but understanding why is a huge step.

However, you stated your case, and I assume she understood. I'd chill on it for now. This is, I'm sure, bringing up old emotions and anger/fear/distress in W, so let her get those settled down.