My immediate response to the book is, "wow! How come I have never heard of this group?" The Family was a group closely related to the Jesus People movement during the whole hippie era of America and was very anti-establishment. It considered The System to be evil and run by the devil.
Though they claimed to believe in the inerrancy of Scripture, their doctrine, theology, and application of that affirmation is mistaken. Their biggest mistake is their submission to the founder of the cult: David Berg. Berg essentially became almost a messianic figure in the movement. His letters, books, and words were elevated to inspired and led his followers aways from Scripture. And as with any cult, whenever an individual is elevated like Berg, heresy is close behind (if not already existent).
But perhaps one of the most horrific aspects of the Children of God is their practice of open sexuality. In fact, they encouraged women to utilize their good looks and their ability to seduce men in order to witness to them. Women, then, would have multiple partners as an act of missions. But their obsession with sex, which started with Berg's cheating on his wife and his multiple sexual partners, doesn't stop their. It seems that members of The Family would swap spouses and relationships and have sex with one another. The sexual sin is rampant among this group.
Since then, the group has become much milder in their sexual promiscuity especially since the death of Berg. But their practice of such sin remains illustrative of their heresy. And as you might wonder, the spread of STD's became a major issue within the group (not to mention the question of pedophilia).
Chancellor has written an excellent book on the subject that looks at the history, teachings, and important aspects of the faith. Anyone interested in this movement should start here and they will be well on their way to fully understanding this bizarre movement.