I started and was already quite disappointed. The code isn't very pythonic and not PEP8. And the explanations are plain bad. I'm still at the beginning though (just started chapter 4). But there are places where I could disagree. How is adapter a way to make "two incompatible interfaces compatible" p57? I feel like the adapter is more about modifying an API (notice the I in the API word) so as to make it compatible, thus just 1 interface. Also, stating "a structural design pattern focuses on providing a simple way of composing objects"p57 seems kinda misleading to me since composition is a strong well-defined notion in CS and shouldn't be used in common sense (is it the case here?). Anyway, I'll read on and try to make the 40€ worthwhile, though I highly doubt it.