I was reading an EPUB on my Kobo Glo perfectly fine last night and then I noticed the battery was low so I exited out of the book and it gave me a low battery warning and instantly went to sleep with a screen telling me to charge it, I guess the battery was lower than I thought it was. So I plugged it in and left it charging while I slept and then when I woke up this morning I went back to reading the book to find it only had 1 blank page, so I checked all my books and found that all of the EPUBs and PDFs were the same (Kobo EPUBs and CBZs are still fine)
I tried removing them and adding them again with Calibre but that didnt help so I thought maybe it was the Micro SD card but adding them to the main memory didnt fix it either
[edit] I just tried adding some books that werent on it before the battery died and they dont work either so it's definitely a problem with the Kobo Glo and not the books