You can download a collection of thousands (maybe a million I don't even know) of books in Spanish in epub format, from the "secret library". It's like a 100Gb torrent, but way worth it.
Ebooks tens to have long lasting battery. I spent a few hours reading on monday.
Just now I'm on my phone, but if you are interested let me know and I'll try to find the link and will mp it to you if you want.
And just now I've been thinking that epubs being so small size maybe there's a way to transmit them over this radio mesh networks on demand, like some sort of radio library. I've have to look into that. Maybe they are too big for that as radio bandwidth for data transfer tends to be incredibly small.