Computer architecture a quantitative approach 5th edition.

Is there a key to understanding this textbook? It is very vague in its explanations of any of the topics and none of the questions seem to line up with any of the information presented in the chapters. They all require huge amounts of previous knowledge and huge leaps to even remotely justify the answer. Is there a supplemental text to this book that provides that background? I am finding it hard to learn anything from this book other than how to spend hours looking things up online to understand any of the concepts presented. Any advice would be greatly appreciated.