The first thing you need to know about ebook DRM is that it can't work.
Like all DRM systems, ebook DRM presumes that you can distribute a program that only opens up ebooks under approved circumstances, and that none of the people you send this program to will figure out how to fix it so that it opens ebooks no matter what the circumstances. Once one user manages that, the game is up, because that clever person can either distribute ebooks that have had their DRM removed, or programs to remove DRM (or both). And since there's no legitimate market for DRM – no readers are actively shopping for books that only open under special approved circumstances – and since the pirated ebooks are more convenient and flexible than the ones that people pay for, the DRM-free pirate editions drive out the DRM-locked commercial editions.
What's more, books are eminently re-digitisable. That is, it's very easy to retype a DRM-locked ebook, or scan a physical book, or take screenshots of a DRM-locked ebook, and convert the resulting image files to text. Google has scanned some 16 million books in the last few years.
It's a solved problem.
Full story at The Guardian.