There are explanatory papers that can sum up things far beyond what crawling through each man page would bring. That being said, there is (at least in the 9front project), a man section called "intro" that skims over most of the technical details and focuses rather on concepts and the basics.

To help in transition should you, or someone else be interested, here are some helpful links: http://www.plan9.bell-labs.com/wiki/plan9/UNIX_to_Plan_9_com...

http://www.plan9.bell-labs.com/wiki/plan9/FAQ/index.html

https://code.google.com/p/plan9front/w/list

http://doc.cat-v.org/plan_9/