Although this book is supposedly about "API" and "Architecture," it does not focus on any topics. It describes in little detail some concepts related to APIs, even with some examples that resemble real-life situations, but leaves further research to the reader. There's no depth similar to Software Architecture: The Hard Parts or other books where you could understand how one would address various scenarios, which are pretty complex. All laid out in Mastering API Architecture can be found on the internet in 5 minutes. So it's a good starter book, but no more than that.