I haven't actually used it, but from what I read it's not a crypto flaw allowing the data to be extracted, but more analogous to the "analog hole". The existence of on-screen readers allows software to be written that walks through the book a page at a time, and rips the content in that way.
It's a bit cleaner than that -- it gets the decryption key from the reader with the Windows debugging APIs, and then removes the DRM. You're left with the original ebook.
I haven't actually used it, but from what I read it's not a crypto flaw allowing the data to be extracted, but more analogous to the "analog hole". The existence of on-screen readers allows software to be written that walks through the book a page at a time, and rips the content in that way.