It also has a dvd with it with video how tos and tools etc. I like the way it has detail from a specification/standards point of view, some real world knowledge from Scott and also good breakdowns of technology-even vendor specific detail/data. It has saved my bacon on several occasions and also made me appear smarter than I am on others
check out the website: www.upgradingandrepairingpcs.com  

I second the suggestion for Mueller's book. It's been a reference that I've kept updated on my bookshelf for many many years now.