Playing to Win has been the competitive gamer's bible since the year 2000. It's been linked on far too many gaming sites to count. Ultimately, it's about continuous self-improvement and getting rid of hangups that get in the way of you winning.
Also, it's not advice for everyone; it's only for those interested in winning.
The entire book is free to read here on the web.
If you'd like to buy it or contribute, there are several options to the right.
The Art of War
Advanced Player's Guide
Elite Player's Guide