Basically, it's an inverted scanner compared to normal designs. The base unit is simply an easel that can be set up at a 45 degree slope (which minimizes the desk space it uses if you're just scanning papers) or laid flat. The actual scanner is the "lid," which can be used on the easel or on its own, or turned upside down and used like a normal scanner. I was afraid there might be problems with light from other sources, since there isn't an opaque lid, but so far this has been fine. Colour rendition has been good.
This first picture shows the scanner on the easel.
For my purposes the preferred mode is to put the whole lid on top of a book. Since you can see the page as you set it up it's easy to get alignment right, and it will hopefully do less damage than repeated scans and tweaking to get correct alignment. These next two pictures show it scanning.
The obvious limitation of this mode is that a thick book will probably need some support one side or the other to keep both pages against the scanner. I can think of various high-tech solutions to this, such as using a laboratory jack to adjust the height on one side, but the easy one will probably be to put another book under the side that needs supporting - I have a lot of books so not a problem. I think it may also be a bit more vulnerable to dirt etc. than normal scanners since the surface isn't protected, but that's what cleaning foam is for.
There's also a negative scanner accessory which I haven't tried yet, not quite sure how it works but it has to be used with the scanner inverted. I don't have any negatives or slides handy to test it.
Overall, I think it's going to be a bit of an improvement, probably not as good as a dedicated camera-type library scanner, but better than ordinary flatbeds. It's also somewhat faster than my old scanner which is nice. The bundled software is adequate without being inspired, but 99% of the time I'll be using Omnipage, which has its own user interface, or capturing images into one or another graphics program, so I doubt it'll see much use.
Count me cautiously pleased anyway.