What is your biggest pet peeve in books?
Probably books published before they were ready. It doesn’t matter how seasoned of a writer you are, you need to have your work professionally edited by a copy-editor, at the bare minimum. I’ve read many really good stories that I couldn’t fully enjoy due to improper punctuation, spelling, grammar, etc. There are many incredibly well-done self-published titles out there, but self-published books tend to have a poor reputation due to some in that side of the industry cutting corners.
I also dislike the newish trend of serial books. Not a book series, like Lord of the Rings or The Dark Tower, but serial books – where the author takes what should be a single novel and breaks it down into a set of small novellas that don’t really stand out on their own two legs. It seems like an obvious money-grab to me. Many of your potential readers will see that for what it is and not appreciate it, and possibly not buy your books. If your story is 500 pages long, publish a 500-page novel instead of five 100-page novellas.