Are they nuns?

Has anyone read these Sister Chicks books?  I think there's a series. 
Somebody on another message board I passed through mentioned them and
said they were great books for christian women but I'm hoping for more
than one opinion before I get myself invested in a series.  :)

This was the link that was posted elsewhere:

http://216.176.197.173/cbot_sisterchicks/index.cfm


Plus - are they nuns or just "sisterly"?


- Robin