Thanks for the replies, good useful information

. I'm surprised that I cannot sideload books using Calibre and a USB cable. Not sure I'll have wifi/internet access where I'm going to for ten days.
To be honest, kindle's vocab builer, superior (stock) dictionaries and syncing for sidelysded books is very tempting, however much I prefer kobo's library management. But the 7.8" screen with the need red lighting...
Will read a bit more tonight