Understanding Patholigcal Demand Avoidance is a fantastic book.
Some children with a diagnosis of Autistic Spectrum Disorder can display extremely rigid behaviours. In these circumstances sometimes strategies typically associated with ASD don't seem to work and in some cases can make behaviours worse.
It's taken a long time for PDA to be recognised as a condition or even perhaps a strong trait amongst other autistic tendencies.
Our son is particularly resistant to change or to transitions and sometimes will just completely refuse to do things or comply with reasonable requests. No degree of bargaining or standing your ground will work and there is a big danger that taking a conflictive action will make the child increasingly frustrated and angry.
Looking back, many of our extreme meltdown situations may have been exaggerated by us trying to follow strategies advised by professionals who didn't fully understand our sons condition nor the reason for his behaviours.
This book explains PDA brilliantly and I would strongly recommend it.