Interesting stuff on the Lafferty brothers and on the modern fundamentalist groups (no idea how accurate that stuff is).

However, his grasp of Mormon history is very tenuous, and he makes some smooth leaps over very rough logical terrain; so smooth that you don't always catch them at first.

His central point is interesting: That religion and belief in revelation is irrational and can easily lead to violence like the Lafferty killings, 9/11, Mountain meadows, etc. In fact, he argues that obedience to a revelation that commands violence is actually rational. However, he completely ignores the plentiful evidence to the contrary, and compelling arguments that counter his.

FARMS and FairLDS have some good reviews of the book. Read the book, but don't take his word on LDS History, and read these reviews, too.