What was the book and what specific point about its message made you two disagree so strongly? I've had talks like that where you realize you're reading two totally different things into the same story, and it gets heated because it feels personal. Was it about how a character was meant to be seen, or the main idea the author was pushing?
Seriously? Missing a meeting over a book talk shows you both actually cared, which is way better than small talk. Maybe @the_andrew gets that a real fight means the story mattered.