It indeed looks cumbersome (reason why i initially put the word between " ") but as i said, one can compare the entire process (registration/validation against the server) to those that we experience with other softwares like Adobe CS suites or any other single application we have a valid registration key for. They all (almost) contact the developer remote server for various reasons : update checking, validation request, etc... and they do so in a transparent way that is barely noticeable from the user point of view. Of course when there is a pop up notifying us about a new version, we know (or not ?) that something must have taken place in the background.
This do not stop people from buying legit copies of those applications.

But its rather a good news to patch the system, is it ? The main thing here being the silent communications between the application and some remote servers.

If it can be printed, it can very easily be converted into a protection free PDF.
The vendor can disable printing all together.
One thing that can be done is screen captures. A few pages book might be easy to handle. However, those around 100+ will put off a lot of people, i think.
The trouble to hack it is way over the purchasing value, most of the time. Trying to hack such a stuff for the sake of hacking (and not for usage) could prove an excellent motivation in a learning curve.

PS: keeping in mind that those secured Ebooks are not installed locally, but might yet be possible to hack.