Ereader

Better than you'd expect, because most of the power draw on most Android devices is the screen. I'd recommend keeping airplane mode on when you aren't using it, because that's probably the next biggest, but on my Max it's generally pretty seriously long, both in terms of reading time and sleep. Admittedly that's a lot bigger, so a bigger battery, but I go through stretches of a lot to almost no activity, and it might be a month since I last touched it, just sitting on a shelf. I pulled it out at 25% just now.

The benefit of Android (beyond choosing your reader app for content you own) is that you can use other apps that don't give you DRM free content you can move around. Libby and Hoopla are two that many US libraries support that will allow you to borrow books entirely for free, I use scribd which is a paid subscription service for a different library of books, and other platforms for purchasing content that is locked down (I don't agree with it; but it's a reality), pretty much everyone relevant has an android app. Same with magazines, news, and sports content that's shorter but more time sensitive. And if you choose to pirate, you can do that right on the device as well in a lot of cases. After experiencing Android on an ereader (even though I can't stand it on a phone), there's very little chance I buy one with anything less again. It takes some tweaking here and there, but there's just too much I would have to give up to go back.