I've been watching the progress of the Mark Twain project over the years, and was excited to know the the Autobiography was being published this year. I ordered my copy from Powell's early this month and got it within a week. From reviews I've read there really isn't much of the much vaunted info that was not to be published until 100 years after Samuel Clemens died, since many researchers and writers have worked through it in the intervening years. However, it should be the authoritative version.
Today the New York Times reports that it has gone back to press numerous times already (the official release date was just last week) and is the holiday sell out book of the year.