Weirdly I think it’s the opposite, pretty sure they have large batteries when compared to screen size

Start by defining your available power. How many watt-hours can you generate? A small 100W solar panel can provide an average of 400Wh of energy per day in the winter. That's more than enough to run a 10-inch tablet 24/7 and LED lighting at night. I've seen 360W solar panels for under $100 on the used market. That's a couple of KWh a day. Even a 100W bicycle generator and a 30 minute workout would power a tablet for 8 hours.

If power consumption is that big of a factor, perhaps separate devices for video, music, and reading would be beneficial. A dedicated music player can consume less than a watt. An e-paper reader requires fractions of a watt.

I have a folding 100W panel, a 30Ah 12V LiFePO4 battery, and a charge controller that I use while car camping. It keeps all the electronics running for a group of 4 without relying on a noisy generator. The battery is big enough to compensate for a couple of rainy days.

My backpacking setup is a 15W panel and a 30Wh battery. That kept my phone and flashlight charged for 2 weeks on the Pacific Crest Trail.