I own the 1998 edition of The Triathlete's Training Bible, which I find an excellent resource. When the new edition came out, I wanted to see the new information, but I didn't a) want to reread everything I had already read and highlighted, and b) shell out for another full edition when I expected over 95% of the material to be unchanged. This companion fit the bill perfectly. It is a slim book (116 pages). It was about $10 which for the amount of the material is a bit high, but considering that the alternative is over $20, and the quality of the information, it is a good choice.
Note that you ONLY want this book if you own the earlier edition of The Triathlete's Training Bible. If you own the current edition, you don't need it and without the earlier edition you would be getting an update to something you don't have -- this is NOT intended to stand alone. If you don't have either edition, buy the new one and you don't need the companion.