I have two. The Ritual and Drowning.
The Ritual is pure smut. 61 chapters and every one contains a graphic, demeaning sex scene. I’m convinced the author was an adult film screenwriter and decided to try their hand at writing a novel. There isn’t a single likable character in this book.
Drowning isn’t a great work of literature. I felt that the characters were very two-dimensional. I hated how naive the author made the protagonist. It made me have a lack of sympathy for her. The ending was series finale of Dexter bad.
A local one my family member bought on a book fair. It was soo bad. It was supposed to be a crime-comedy but wasn’t too funny. There were more food descriptions than actual action. When I thought something was about to happen, it then got described as “I met X and she told me she took care of the problem” with even more descriptions of food they ate. Language and descriptions suggested the book was written by an alien who learned about humans from an alien textbook. Of course it was self published. I felt really bad about rating it 1/10 after seeing the nice author in person (and the book had close to no reviews), but some things should never be published.