And it doesn't look like they ever will be. Most likely because of the constant flux of copyright laws in the US. While the books are public domain elsewhere (Canada and Australia, for example), because of the screwy ways the current U.S. copyright laws, nothing new was added to the public domain in 2010, and it doesn't look like anything will be entering the public domain in 2011 either. As it stands I can buy the remaining two books off of Barnes and Noble for my NOOK without issue, it's now tracking down a copy of The Blythes are Quoted that's becoming a bit sticky. Apparently it was published in 2009 in a limited run. I can't find it on Barnes & Noble or on Amazon. Well, scratch that, I can find them, but it's either ridiculously overpriced or has to be imported. Seriously Canada, why are you holding out on us?
At any rate, in my constant quest for literature, I find the public domain a rich source for reading material, but sometimes there are titles that I want in particular but can never have.