I finished a book recently that ended with a cliff hanger. It was the second book in a very, very successful series. I don't think I have ever read a book that has ended in a cliff hanger before. I always thought it was one of those things that authors should never, ever do. It just goes to show authors do not have to always follow the "rules" of writing set down by their peers.
As I was growing up, I did alot of research about writing on the net and I learnt many things. I was told not to "head hop" between characters (writing from one persective and then changing to someone else) or to start a scene with description, write in first person, to avoid certain words and of course to never, ever end a story with a cliff hanger.
I have followed most of these rules and I have found that my writing has improved. I am so much better now then I was years ago. Some of the rules I think are stupid. For example the do not write in first person one. One of my favourite series is the Stephanie Plum books and they are written in first person.
I love it when writers "break" these rules and chose to be different. I have written books where the author has done the opposite of 'show don't tell' and written pages and pages of backstory or an 'infodump' as writers call it. I have read books that had chapters that were a single line or a paragraph long. I've read stories that were one endless paragraph with no commas or full stops. When authors break the rules they stand the chance of creating a written work that is terrible and difficult to read or something so different, so outrageous, it will become a beloved classic. Maybe one day I will write a book with a cliff hanger and see what happens.