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.
Any book written by a politician or pundit. Atlas Shrugged, any corporate self help/motivator books. Plenty of sketchy “history” books as well, but I may not recognize them at first glance.
I’d be super accepting of any and all dumb kiddy/YA novels or “low brow” books, comics, anything like that. Fun is fun and I have a small section of my shelf dedicated to such frivolities.