This is a book for someone building their first PC, which was my position - although I'm certain to dip into it for my 2nd and 3rd (yes, be warned, the process is slightly addictive).
The documentation you will get with your motherboard is pretty good, though the images are likely to be small B&W rather than the nice big colour illustrations in the book. However, where this book scores in particular is helping you think through things like "what kind of PC am I about to build?" (budget, mid-range, top, media centre, storage unit etc).
Having decided roughly what you want, you will then be presented with options such as alternative CPU units that would do the job, the type of motherboard you should use, what graphic card you might want ... You will also be talked through installing drivers and operating systems, what free-ware there is out there that you might want, and a trouble-shooting checklist.
I refurbished a Dell Inspiron 3000 with a new motherboard, processor, memory, and hard drive. What was left you might ask, but I do now have a useable power supply for spare, and was able to reuse the case, the graphic card, one hard drive, the keyboard, mouse and monitor. The result is a very nice and *much* faster computer.
I can recommend this book. Well worth the price and a good confidence booster for a newbie.
PS -- Have a look, though at motherboard sites too. On the Gigabyte site there is a fairly complex, but very useful ebook on building a computer that is a free PDF download. For me, though, this was a "as well as" rather than a substitute item.