Mike, take a look at the chapter on the ending in James Cox's
-_Mark Twain: The Fate of Humor_.  Also, I have to agree with the
other Mike's assessment of your reaction to the verb "deconstruct."
Deconstruction is not something new, but a new description of
a rhetorical activity that is very old.  I think the idea that Twain
"decenters" his novel in the ending, thus robbing the reader of any
sense of self-righteousness that may have accumulated alnong the
river, is consistent with Twain's methods in several other instances.