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.
Since so many people have beaten me to Ayn Rand, I’ll go with Terry Goodkind. A dozen and change novels of turgid, terribly written doorstops which amount to Objectivism for Dummies, set in a world which is a cheap knockoff of every other 70s-90s fantasy you’ve read.