The only advantage of EPUB is that anybody can sell you a DRM-ed book, because there's a unified public way to do it. This allows for a separation of a device and content provider. I'd say device manufactures might be tempted to go for Amazon model and be both, but none of them is such an imperium like Amazon, which also had a head start and is now where it is because of it. Amazon is the only one that can legally provide DRM-ed content for Kindles. There are places where you can buy non-DRM content for Kindle, so they rely on kindness of their customers not to share their books with other people.
I got The hitchhikers guide to the Galaxy last week for my Kobo and was surprised to see no DRM.
i know it is a old book, but I have listened to the radio series, even got the books on tape, watched the TV series, watched the film, but I have never read the book.