I’ll go with the low-hanging fruit: Mein Kampf. I’ve read it, cover to cover. As a piece of propaganda, it’s good. As an example of good writing? Absolutely not (though I will admit I have only read it in translation). Oh, and the whole fascist, racist, and generally shitty worldview of the author that he infuses into the text. And the fact that the author is literally Hitler. You 5-star that book? You’re a Nazi. Period. And as a Jewish person, I don’t look too kindly on them.
I think it’s good, and it’s helped me with some conflict resolution and getting better at being who I want to be socially, but it’s not a 5 star book except in it’s own category, where I would say it’s one of the best self-help books because it doesn’t advocate anything unethical that I can recall. But I think anyone who rates a self-help book 5 stars with no qualifiers has definitely made that book’s advice their whole personality.