I did my searching based on music/CDs since the wording is a lot more clear, but the same rules apply since were still talking about copyright infringement.

As long you’re making the copy for personal use and aren’t selling/distributing, you are fully in the clear:

• It’s okay to copy music onto special Audio CD-R’s, mini-discs, and digital tapes (because royalties have been paid on them) – but not for commercial purposes.

https://www.riaa.com/resources-learning/about-piracy/

As far as ethical, this is mostly up to you, but unless it’s from an independent artist/distributor, I personally see it as: if you were never going to be a customer to begin with, they're not losing anything. I am, however, against then reselling it yourself. Ymmv.

who cares, do it anyway

Most countries consider this "private copying" which is legal. Not a lawyer, you should check your country's laws.

Unethical? Copying is not theft.

As long as you don't distribute it it should be fine legally (in the US) and is morally correct (imo) since it is your own copy of the book.

It is legal but in any case why do you care. If it were illegal it's not something that would be enforceable or something they'd be likely to "catch" you for, and it's definitely not unethical. Everyone should be free to do whatever they want with published literature.

Ethics and legality are far from the same, or even linked.

I imagine it'd be the same as printing of a copy of the Mona Lisa and putting it up on your wall for your own viewing pleasure. Completely legal.

Where as printing it off and then charging other people to see it would be illegal.

As long as you don't distribute it it should be fine legally (in the US) and is morally correct (imo) since it is your own copy of the book.

Ethically you can make as many digital or physical personal copies as you want for yourself outside of perhaps a concern for wasting resources but if you sell them you're taking away earnings from an author or rights holder or owner which may each have different moral weight and require recognition of property rights as a thing worth having. But if you're caught with hundreds or thousands of copies or copies where they are easily accessible to the public it's going to appear pretty suspicious.

You are legally permitted to do so, but not entitled.

What's the difference? DRM.

If you license a digital work, you are allowed to make copies for personal use. However, if the publisher includes features to prevent replication, you are not entitled to make a copy; in other words, publishers including DRM to prevent replication of their works is not illegal because you do not have a right to copy digital works you license, but you are allowed to do so.

If it wasn't fair use I'm sure they would have gone after Kurzweil (popular assistive technology program designed explicitly for scanning books) a long time ago