I'm not sure I understand - is TAOUP bad because it stole information, or because the information it has is wrong?

Because I'd consider the latter to be far worse than the former.

I enjoyed it when I read it many years ago, but maybe that was because I was inexperienced and naive.

Could you recommend some "original sources" to learn from, instead? Ideally in book form?

Not TAOUP specially, but the Jargon file is what ESR took loads of things as wrong or Unix related. Also, at TAOUP you have Emacs, which is the Anti-UNIX by definition. https://www.dourish.com/goodies/jargon.html

TAOUP had a chapter "a tale of 5 editors" discussing emacs, vi, and more, and does point out emacs is an outlier (and outsider) to many unix principles. It does quote Doug McIlroy speaking against it (but also against vi?). It attempts to generalize from discussing "The Right Size for an Editor" question to discussing how to think about "The Right Size of Software".

I don't know if it's possible to have impartially "fair" discussion of editors. Skimming now, I can see how vi lovers would hate some characterizations there. But it does try to learn interesting lessons from them.

It does NOT simply equate "Emacs has UNIX nature" so you can't just prove something like "TAOUP mentions Emacs, Emacs is GNU, Gnu is Not Unix => TAOUP is not UNIX, QED" ;-)

http://www.catb.org/esr/writings/taoup/html/ch13s02.html

bias disclaimers: I learnt most of what I know of unix from within Emacs, which I still use ~20 years later. I learnt more from Info pages than man pages (AIX had pretty bad man pages). I suspect you have a different picture of unix than I. And I now know better than arguing which editor is better ;)

But I found TAOUP articulated ideas I only learnt through osmosis. I'm looking forward to reading a better articulation if you know one.