[throwawayffffas]

I think it's very similar in both countries, but you have got it wrong. Downloading a book without permission is copyright infringement in both countries, regardless of whether you distribute it.

In the UK it's a criminal offense if you distribute a copyrighted work with the intent to make gain or with the expectation that the owner will make a loss.

Gain and loss are only financial in this context.

Meaning that in both countries the copyright owner can sue you for copyright infringement.