The very first book I ever read on the subject was a long time ago:
Boundaries Where You End And I Begin: How To Recognize And Set Healthy Boundaries by Anne Katherine
It's been years since I read it....so maybe you should check the reviews on Amazon to see if it might be what you are looking for.
I do not recall a religious perspective at all, and I do remember getting some great insight.
I think the religious book(s) you are referring to, is the Cloud and Townsend series. I found those books incredibly helpful, even with the religious perspective.
[This message edited by refuz2bavictim at 2:10 PM, November 19th (Tuesday)]