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.
My grandma has the Dianetics book. Apparently she was involved with Scientology for a while? Sadly, no one ever told me the truth (one of those things that when asked about, everyone changes topics) and sadly she now resides in a jar, the only way of asking her directly is through a oujia board.