Books

I think it depends on what you want. You only need to do the SQL lite thing if you want to be able to access the store and overdrive, probably a few other features.

If you don't care about any of that, you just open the .conf go to the [ApplicationPreferences] section and add the line

SideloadedMode=true

Then you're good to go. This worked on my Kobo Clara BW and my old Libra h2o (which I miss so much).

If you want to keep going from there then nickelmenu, koreader.