The EU Court of Justice has just ruled on this issue per this other thread here:
https://www.mobileread.com/forums/sho...d.php?t=233365
It appears DRM removal is fine as long as it does not result in sharing a file with anyone else.
If you do it for backup, that is alright. If you loan the stripped file to your brother, you have violated the law. Of course, this just applies to Europe, not the US, Asia or any other location.
I am going by the interpretation in that thread. It will take an attorney here to read the link from there and render an opinion here to really understand what just happened. I am NOT an attorney.
The link to the actual decision in English is here:
http://curia.europa.eu/juris/documen...rt=1&cid=39073
By the way, that appears to be a PRELIMINARY ruling. A final ruling will probably be released in a few months.
If my interpretation is correct, it appears the Amazon way of securing song files is the best so far and should be applied to books. They issue unprotected song files with a 9 digit serial number in the metadata.
If authorities inspected someone's PC for totally unrelated reasons and found recently dated files without the proper serial numbers, than an example could be made of that person if he could not explain the reasons for it. If serially numbered files were found in sharing sites in case of a raid, they could be traced back to the uploader.