After digging&asking around, I've found the following pictures, UPDATE Onyx unleashed, the wacom screen is indeed behind, as Harry has stated:
It has sophysticated sensor system, emitting EM waves, that feed (!) stylus, that responds with god knows what kind of positioning information.
Advantages of this technology:
- Does not degrade the screen
Disadvantages:
- Works only with special stylus, fingers won't work
- Longevity
Not sure about battery life.
Here are photos of iRex DR800SG (also has mentioned kind of touchscreen) vs many readers:
iRex vs 300
iRex vs Kindle (?)
iRex vs 900
iRex vs 505
iRex vs Nook