As salaamu alaikum,
An excerpt from the book:
“It was impossible in the Call of God to disagree with the leader and remain faithful. That disagreement with the leader was the equivalent of disagreement with God. This thinking then provided the leader with absolute authority and no meaningful accountability. The only way a member could sustain disagreement would be to leave the group entirely, and there was no legitimate reason to leave. Also, there was nowhere to go if the person left, because there was no equally viable alternative group anyone could identify. Only the Call of God had the truth, and everyone else had somehow fallen short and was in some way wrong. Any member who chose to leave was therefore not only a spiritual failure but also one separated from God and lost, according to the group.”
Pay attention to the signs when you see them!