1. when author's styles change from 'interesting and different' to 'ewww get me out of here'. like stephen king for one. so, i end up picking up one of that author's latest books, thinking it will be just as good if not better than the previous one, and it gets... gory.
2. and i know this is my issue but typos and incorrect word choices drive me crazy. it's a book, it's published by this big publishing house, i'm sure they have plenty of editors and proof readers on staff. Use them! I know it's not possible to always find every mistake, but sometimes books are just sloppy and it's annoying.
So agree about King.
Carrie was one of the first true horror novels I read and it was so unusual in its style (the magazine and newspaper articles interspersed with the prose) that it kept you reading just to see what magazine he would include next. Ditto
Salems Lot and
The Shining.
And then, somewhere down the line, I want to say the book was
IT, things went from being horrific love letters to Maine and New England and turned into ruminations on people's bowel movements, gore and gore and gore, and all kinds of references to bodily fluids. Instead of the compelling, irresistable feeling of "what happens next" I remember being treated to one character's thinking about his constipation for several pages in
IT but delivered, not in that character's tone of voice (which would have been more circumspect, I think) but in King's very snotty tone, as if he was mocking the character who would ultimately prove the real hero of the story.
I haven't been able to read his new books since then.
Regards your second point: I have a friend who is a proof reader for a couple of houses...and it's a very frustrating job for her. She received an instruction from the editor of one rising romance star saying "Do NOT correct the grammar or the spelling. Do NOT point out holes in logic. We don't have time to fix them." She says "They pay me to read this trash, but they won't let me fix what's wrong because it'll cost them money. If I didn't need the job, I wouldn't do it." (Among some of these gaffes is a woman who is simultaneously putting on her high heels, while zipping up her dress AND walking out the door. Or there is the plot in which a woman kidnaps a pilot to get her to an island where her ten year old son will be sacrificed to some evil God or other....as his father was before him, in fact, ALL first born sons of first born sons are sacrificed at the age of ten. Sooooo, question: how did her husband survive long enough to grow up, get interested in girls and find HER. Corollary: if you are sacrificing these children at age ten, and each one if the first born son of the first born son of this one family line (clearly stated), uh---how do they keep begetting first born sons of first born sons if the first first born son was killed at age ten?)
She's had me read some of these treasures and I want to scream. And THAT is why so many books are filled with errors. Apparently first readers are used to see if the writing makes them bleed from the eyes and when it doesn't, they send the book to the publisher.