Excellent book. It really helped me in my first PC build. Thorough description of all aspects of Building a PC. Excellent description of component selection. Great step by step guide to the PC build. A very good overview of post build procedures including: creating floppy boot discs, setting up raid and partitions, installing and setting up drivers, optimizing performance, maintenance, benchmarking, etc. However, the book would have been more useful if it had included a more thorough and extensive overview of Installing Windows.
ExtremeTech also published a companion book called, 'Build the Ultimate Custom PC' which does include a thorough overview of installing Windows, but it's not as thorough (in other aspects) as this book. It would have been nice if ExtremeTech had combined the 2 books into one more complete book. But as it is, Build the Ultimate Gaming PC is the best book that I've read on building a PC and I've read 4. It's relevant to building a PC for any purpose, not just gaming.
I also found a great DIY Guide to Building an AMD Socket 939 PC at HardwareZone.com. It's a little dated (summer 2004) but it's thorough, well written, easy to follow and free.