You can side load on all readers I believe. Kindle, Nook, Sony and Kobo as well as iPhone/iPad comes with their own eco system, all other readers are dependent on side loading for their existence. I believe the norm is that you connect through USB and then the device is treated as an external drive. The only device, and I'm not entirely sure here because I have never used it, that might not have side loading is the iPhone/iPad, but that can probably be solved by uploading books to an iTunes account and then receiving it from there. Someone using those devices should be able to clarify.
|