That's why when I was looking to buy an e-reader I settled on a PocketBook. Yes, the Russian ones. It's the most-open e-reading device I've seen. You literally just plug it into your pc with a standard USB cable and it appears as a normal drive that you can upload whatever you wish to. Including normal binaries. There's no rooting steps involved or anything, it's plug-and-copy-an-ELF. It runs a normal everyday Linux.

There's a vibrant community (though you might need to be somewhat familiar with Russian) of all manner of customization possibilities and different applications you can install.

It also comes with snake.

When they start offering A4 devices, I'll definitely buy one (unless someone gets an incurable brain tumor and makes them closed).