It's not a hugely useful bit of information, but I found out a while ago that most Kobo eReaders are able to handle ZIM files. And some of them can have their

It's not a hugely useful bit of information, but I found out a while ago that most Kobo eReaders are able to handle ZIM files. And some of them can have their "on-board" storage increased, which is actually a normally non-user-accessible SD card. I wouldn't do it on a water-resistant model to avoid breaking the seal.