“renting” it is still taking money from the author even if the damage is physically limited to one item.

I do see where you're coming from, but not necessarily. If my friend has zero interest in ever buying said book (or can't afford to) and would never become a paying customer, there is no downside to sharing a copy. In fact, if they like the book enough, they may even become incentivized to buy themselves a copy or look into the author's other work legitimately when they otherwise wouldn't have.

This is how/why I pirate most games. I don't have the type of pocket money to spend on games I don't know I'll love, so I pirate them first. If they're good enough, I'll buy the actual game on steam later. Spider-Man, Baldur's Gate 3, Cassette Beasts, etc. are all games I plan to buy when I can afford to. And I can promise I never would have bought Slime Rancher 2 if I hadn't pirated the first one at some point and enjoyed it.