Wired’s Gadget Lab has a feature profiling a new, specifically-for-books flatbed scanner, the Plustek OpticBook 3800. The defining features of this scanner seem to be a thin bezel that allows all-the-way-to-spine scanning, and a specially padded liner to eliminate distortion.
I’m actually a bit surprised that Wired is so excited over this scanner, given that in the last couple of years we’ve already seen a number of book scanning apparatuses (both do-it-yourself and commercial) that leave a one-page-at-a-time flatbed in the dust. The future of non-destructive book scanning seems to involve digital-camera rigs that can snap shots of two facing pages at once, without requiring careful arrangement of each page. (And, as someone brings up in the comments to Wired’s article, if you don’t care about keeping the paper book you can just cut the spine off and sheet-feed it.)
The point you missed is the overhead cameral solutions are 2 to 10 times the costs.
It’s also a product you can actually buy; the other apparatuses you point to all seem like vaporware for now. I don’t have the 3800, but I bought the 3600 a little while back. Once you figure out the (rather clunky) software, it works pretty well; I use it to turn paper books into PDFs which have excellent typography, layout, proofreading … and no DRM 😉
The Plustek has been around for years, and has always been wildly overpriced. The best solution for book scanning is to cut off the spines and run the pages through a cheap multipurpose printer with a sheet-feed scanner. The time you save — assuming you have a real job too — will more than pay for another copy of the book, if you want one.