Mark McGwire and Jose Canseco--the Bash Brothers--ushered in a new era of muscle-bound power hitters in baseball in the late 1980s. Suddenly balls were flying out of the parks like never before, and the rest of baseball stood up, took notice, and followed suit. Baseball's bodybuilding revolution, with its resultant steroid infestation, was here to stay, and many experts today point to these two players as a large reason why. Author Dale Tafoya has interviewed more than 150 teammates, coaches, scouts, and friends who knew McGwire and Canseco during that era, including former A's general...