[CentOS] Wherefore SELinux?

I've tried to wrap my head around SELinux several times, and so far, all I've 
managed to do is rap my head, and then somewhat painfully. 
		
Is there a detailed "SELinux Unleashed" style book anybody can recommend? 
Anybody read Oreilly's book care to comment? 

Link:  
http://search.barnesandnoble.com/booksearch/isbnInquiry.asp?userid=XS0ILLMCWv&isbn=0596007167&itm=1

(Free resources preferred, but quality and readability comes first!) 

-Ben 
-- 
"The best way to predict the future is to invent it."
- XEROX PARC slogan, circa 1978