My son uses a Kindle DX. I had to replace the battery, it doesn't have WiFi, and they shut down the 3G network access years ago. It's perfect in that way. No distractions and no network access.

I removed the 3G modem when I replaced the battery to prevent it from being turned on and draining the battery as it constantly tries to connect. The microusb port is not in great condition and only works with the cable at certain angles. On the bright side, that's only an issue every few weeks when it gets charged and a new load of books.

My wife has the newest basic Kindle because she prizes light weight over any other aspect.