Can you read e-books through an mp4 player?

I personally don't think you can add ebooks, I've tried using all the ebook files including the one my user manual says to use, it just tells me it's an invalid file. I have a 65$ mp4 player that played music, videos, pictures, tells you the time, has a calculator, lets you manage your files, does Bluetooth, and has an ebook reader, basically a phone with no wifi and no app store. so I do not understand why it can do all of that and not read an ebook file. it has no ebooks on the ebbok reader but the device says it has 2 preinstalled ebooks and it says once again "invailed file". This honestly saddens me because I love to read books but you cant read book and mp4 players unless is a 100$ mp3 player.