As this is clearly off topic for programmers, I will keep this brief. Most books on this subject are either aimed at the professional and contain reams of specifics about chips and pin-outs etc. or they are so simple that anyone who needs something that simple should not even dream of opening their computer. In my opinion, this book hits the happy medium. If you are capable of doing your own upgrading and maintenance then this book is pitched at just about the right level. The author writes in a style that demonstrates that he does know what he is talking about and understands the trials and tribulations that beset those who tinker occasionally with their machines.
Definitely one of the better books on this subject.