Basically, Blumentahl immersed himself in far-right fringe culture for six years and investigated how the Republican Party has been hikacked by extremists, and how more moderate Republicans like Bob Dole, George H.W. Bush or even John McCain have been pushed to the side.
"The GOP has become subsumed by dysfunctional personalities with no capacity for restraining themselves, either from acting out hysterically or from their most devious urges. For these internally conflicted figures, who will continue to produce new and increasingly bizarre scandals, right-wing political crusading is simply a form of self-medication."
Blumenthal partly explains the far right's new vigor by the fact that it functions best when the government and Congress is democratic so they can more easily throw stones form the outside. It seems like a scary but necessary read as one should face the reality of what is going on.