I can never tell the appropriate way to say thank you to a poster here. Should I upvote? Should I leave a comment? In this case, I'll do both.

Thanks for the recommendation, most of the maths work I do these days is financial, so geometry is a nice diversion. I hadn't seen this text before so I've got it bookmarked for some reading now.

As an aside, is this something I would have gotten some exposure to if I'd been a college grad? Any time I see things like this, I worry there are large swaths of text I've missed in self-study.