Hi Albert,
I found your thread and suggested book interesting as this is something that I'm looking into.
My mother was raised RC in Poland pre-war. Her and her parents had typically Polish names. However my DNA has since revealed that they were 100% AJ. I do know that the family of a polish friend of my mum's moved from Rivno further west in 1930's and changed their names in the process.
Knowing now that my maternal family were AJ and having, at present, exhausted trying to find documentary evidence of them in Poland, pre-war, I am considering the name change possibility but can find little concrete evidence of this. 
Does anyone have any insight into this area? 
Noreen Clark (England)
(Szczepanski + Morzowska -  possibly false names!)