Many writers keep a notepad on their nightstand for jotting down ideas they have while sleeping. I've gotten some inspiration from my dreams and sometimes find solutions to my writing dilemmas.
Two of the fiction stories I am currently working on are based on a dream I had. Just a snippet of a scene can create an idea for an entire story. Expand or rearrange a dream you've had to write a novel or short story.
"What Dreams May Come" is a novel and movie about the here-after written by Richard Matheson. This story reminds me of some bizarre dreams I've had. Characters change gender and race. Some of the scenes morph from reality to phantasmagoric. If you haven't seen this movie I highly recommend it. I don't know if it's based on a dream the writer had but I wouldn't be at all surprised.
Our dreams can be written for any genre or reading level simply by changing the perception. A monster under the bed can be described as very scary and horrific for an adult novel or cartoony for a children's book. It's your story. You can mold it however and for whomever you chose.
Stephen King has many phobias and that is one of the things that has made him a great writer. He turned his fears into real stories that scare everyone else. Many of his novels are nightmares he wrote into a book.
Maybe you have funny dreams about shopping in the nude; write a comedy. Or dreams about trying to find someone or something; write a mystery.
Anything you can dream you can write about.
May all your dreams become great novels. :0)