copyright infringement is not theft, even if right holders often claim it is.

part of the definition of theft is that the original owner is deprived of it, which does not apply to copyright infringement.

You can only argue with damages from the perspective of potential profits, still not theft though.

https://en.wikipedia.org/wiki/Theft

Moreover, reading a copyrighted book and learning from it is not theft.

Reread my comment and look for a value judgement on my part. The final sentence is probably a good clue as to my opinion.