I bought this book back in '76 or thereabouts since I wasn't satisfied with the "it's magic!" explanations of how computers worked provided to me back then.
I wasn't satisfied with the "it just works" explanations; I wanted to know HOW it worked, and this book is an excellent treatment of that topic that goes into the "nitty-gritty" of what goes on "under the hood".
Points: 1. It's a bit "chewy" as it does a deep dive into how a CPU works internally - he actually designs a simple CPU as an example - and goes into detail about the various memory, I/O, and interrupt models used in the microprocessors of the day. It might not be interesting unless you want a good theoretical background in computers and computer technology.
2. IMHO it provides an excellent treatment of the "magic" inside of a computer that's still valid to this day. (A more advanced book on modern systems and protected mode processing can be had by reading "Understanding the Linux Kernel" which is also a bit chewy.)
3. Having read it, it provided valuable insights into the nature of computers that has been invaluable to me throughout my career.
Please remember that this book is not for the faint of heart and isn't "casual bathroom reading". It's a serious book that could have easily become the textbook of a college course in microcomputers.
Viewed in that light, it's an excellent treatment of a complex subject.