Here (http://www.subreality.com/marysue.htm) is the site I mentioned before, one of the earlier Mary Sue pages with explanations and appreciation for the kind of role she plays in the writer's development. The site hasn't updated in a long time, but you might look through links and essays.

Relatedly, there's also a fair amount of meta-fiction out there, Mary-Sue and otherwise, and the Subreality (http://www.subreality.com/sc.htm) phenomenon that occurred in comic book fanfiction in the late '90s. You might find it interesting.