Copying music/books

Is it prohibited to obtain a digital book/music for free (when normally it is sold, but someone made a copy of it and publicized it)?

What was the rationale of the person who copied it?

to allow others to read and listen for free

As long as the intention was not to cause harm to the Artist and there is NO CHARGE whatsoever, meaning the person copying is NOT doing it for a business, then it is permitted.
This is clearly the Halacha as ruled by the Rav.

Nevertheless as of late many lawsuits have ensued and it is not clear (at least to our limited research abilities) if in fact it would be illegal. As a result of the possibility of that, the Halacha would dictate that one must follow the law (dina demalchusa dina) even in the event that Halachically its permitted.

I’d like to point out, as a composer and performer, copyright fees is what we are making our living from. Copying in any form without our permission or those who represent us is stealing.

Don’t you need permission from the author/copyrite owner to copy and or distribute?

This may or may not be accurate, as pointed out above. If in fact it is against the laws it would be. If not, it is also not against Halacha

See here for more on this topic.