The only e-reader currently planned to be supported by XCSoar is the Kobo Mini.

Well that is unfortunate!
In the USA the Kobo mini is almost unheard of!
I see you can get it on Amazon for $90, about the same as the Nook. But the quality is not as good. Three reviewers out of 12 said " Don't waste your money on this e-reader. "

Just so everyone knows what they are getting into:
Currently, the method of getting XCSoar to run on the Nook is tedious but do-able with the help of the detailed instructions at the TopHat site. It requires a couple of spare micro-SD cards and about an hour. You also have to do some soldering to create a special junction cable that will connect your GPS USB to the Nook and to a 5V USB power source that plugs into your glider's 12V power. This requires purchasing a few male & female USB connectors, a USB cig.lighter charger and a small On-the-Go (OTG) USB adapter cable to fit into the Nook. A really nice hockey-puck GPS module is available for $31 at DX.com. With the ghosting on the screen, I'm not sure it is all worth the effort. My Streak is very clear in the cockpit.