Virtual machine testing is a good idea, but I wouldn’t rely on it. Well written malware will check for a virtual environment and might even hold off executing if it detects it. Better malware will have already gained persistence as your testing for it.
First, I should note that I haven’t come across (Readium?) LCP before - so I don’t have experience with this particular method for DRM - I do however like to play with these sorts of things and have definitely come across some similar methods, etc.
I found a similar tool on GitHub which may help you to better understand what the process is for figuring out something like LCP: lcp-decrypt. I’m not sure how fresh your knowledge is on encryption - but it would help to have some knowledge of the process you’re trying to reverse engineer.
If you happen to find a sample with of non-copyrighted material that has some sort of encryption you’d like examined, I’d be happy to have a look for educational purposes.
Then ye be needin’ a crew. Argh!