I've been thinking about genre a lot lately - mainly because my own work is often so difficult to classify! I'm not sure how much difference it makes to readership, but agents and publishers very often specify which genres they will or will not publish, and everyone seems to have a bias one way or another. Genre seems like an arbitrary label, but does it affect a book's appeal?
Here are the main genres I can think of (debatable of course!)
Contemporary: Stories set in the everyday world, which explore issues relevant to us today. Contemporary romance is a popular genre.
Fantasy: Broadly speaking, fantasy stories involve magical elements as central to the plot and story world. It can be split into:
-High fantasy, which is set in an entirely fantastical world. Epic fantasy generally involves world-spanning themes and events, often steeped in mythology. Think Lord of the Rings, the Mistborn series, or A Song of Ice and Fire.
-Urban fantasy, in which the fantastical elements are woven into the everyday contemporary world, be it through a hidden magical world, or the story itself taking place in a world like our own but with the presence of magic or magical creatures. Many YA series, such as The Mortal Instruments and The Demon Trappers, fall into this category.
-Dark fantasy, which comprises elements of both fantasy and horror, often overlapping with supernatural and paranormal. Arguably, Stephen King's Dark Tower series falls into this category.
There are many other subgenres, including fairy tale fantasy, mythological fantasy, supernatural fantasy...too many to list!
Paranormal: Involving paranormal elements such as vampires, werewolves, ghosts, psychic powers, etc. Often overlaps with fantasy. Paranormal Romance is a popular sub-genre.
Horror: At its most basic, fiction written to scare the audience, generally involving some aspect of the supernatural, be it ghosts or monsters. Much overlapping with fantasy.
Science Fiction: Novels based on futuristic elements, imagining how technology and science might evolve in the future or in alternative realities. A good example I read recently was A Confusion of Princes by Garth Nix.
Dystopia: Similarly to science fiction, dystopia postulates future realities, but often with the worst possible outcomes, exploring what humanity might become under certain circumstances. There's a LOT of dystopian YA fiction around right now. The Hunger Games, Divergent and Delirium are all great examples!
Post-Apocalyptic Fiction: Often overlapping with dystopia, this genre imagines a world in which civilisation has been destroyed, be it by natural disaster, zombie apocalypse, or war. Examples include Hollowland by Amanda Hocking, Dark Inside by Jeyn Roberts and Angelfall by Susan Ee.
Obviously a large number of novels overlap - and that's why it can be misleading to confine yourself to one genre alone. Obviously you should write what you enjoy, but I personally find that my novels are often a mishmash of fantasy, supernatural and paranormal - with gothic horror and fairy tale elements thrown in as well! I'd say write the book you want and worry about genre later - readers very often aren't concerned with the genre but with the story itself!