From time to time Watford Writers, the Writing Group I attend regularly, holds a Flash Fiction Competition. For ages I did not enter one but recently I decided to participate. To my surprise, writing a short piece of Flash Fiction jerked me out of my comfort zone and opened up new possibilities.
So far, I have only written historical novels but my experience with Flash Fiction has led to my exploring other branches of fiction such as Steam Punk (I have a list of authors whose novels I wish to read).
As a result of the Flash Fiction I have written I took Writing and Selling a Novel - How to craft your fiction for publication - by Marina Oliver off the bookshelf and consulted the index to read what she wrote about genre:-
"There are different sorts of novels. They vary in length and in their emphasis on different aspects, but it's possible to group most of them into recognisable types.
"The genres such as crime, romance, horror, science fiction, westerns and fantasy follow certain conventions and appeal to a restricted readership. So do the 'literary' novels while 'mainstream' have a more popular, general appeal."
Writing and Selling a Novel is well-worth reading.