Pure architecture is the opposite of spaghetti code, where everything is intertwined and there are no separate elements that can be easily separated from the rest and replaced without destroying the entire system. The essence of a pure architecture is to clearly define "what is where and why," and this should be your first priority when designing and implementing a software system, whatever architecture or development methodology you want to adhere to. To fully appreciate the book, you need to know Python and be familiar with TDD, in particular unit testing and mocs. Please refer to the "TDD in Python with pytest" series published on my blog if you need to refresh your knowledge on these topics.