The reason you need to keep up on genres is because they are very important for things like promotion, writing to market, hitting all the right beats by mimicking what makes that particular genre popular among fans, or else avoiding it entirely by creating something original.
Either way you look at it, it's important to have a basic grasp of the mainstream genres out there. That doesn't mean you need to know every single genre before writing. Heck, I only learned about the sub-genre New Adult this year. And when I asked my editor if I should classify my novel as "NA" she asked, "What's that? Haven't heard of it."
This has primarily to do with the fact that NA is a relatively new genre. Not only that, it didn't exist before 2009 and it's still flying under the radar of most trade publishers, only to be used mainly by Indie writers who were the first to crack this market niche.
But it does help to know something about the difference between say and adult novel and a young adult novel.
As such, I decided to adapt this handy dandy Wikipedia post on genre lists and write down the basics of genre classification in an easy to digest format. Hopefully it will be useful for those who, like me, need to pick a genre classification for their novels when submitting their meta-data for publication. Otherwise, it's just an interesting bit of history.
NOTE: Genres and subgenres are organic and can change both in terms of their content as well as their relationship to other genres. Also, new genres and classifications are being created all of the time. So don't take things too literally, this is just a list meant to help ease things along.
LITERARY vs. GENRE FICTION
Literary fiction has been defined as any fiction that attempts to engage with one or more truths or questions, hence relevant to a broad scope of humanity as a form of expression.
There are many sources that help readers find and define literary fiction and genre fiction.
Crime/detective – fiction about a crime, how the criminal gets caught, and the repercussions of the crime
Fable – narration demonstrating a useful truth, especially in which speak as humans; legendary, supernatural tale
Fairy tale – story about fairies or other magical creatures
Fan fiction – fiction written by a fan of, and featuring characters from, a particular TV series, movie, or book
Fantasy – fiction with strange or otherworldly settings or characters; fiction which invites suspension of reality
Fiction in verse – full-length novels with plot, subplot(s), theme(s), major and minor characters, in which the narrative is presented in verse form (usually free verse)
Fiction narrative – literary works whose content is produced by the imagination and is not necessarily based on fact
Folklore – the songs, stories, myths, and proverbs of a people or "folk" as handed down by word of mouth
Historical fiction – story with fictional characters and events in a historical setting
Horror – fiction in which events evoke a feeling of dread and sometimes fear in both the characters and the reader
Humor – Usually a fiction full of fun, fancy, and excitement, meant to entertain and sometimes cause intended laughter; but can be contained in all genres
Legend – story, sometimes of a national or folk hero, that has a basis in fact but also includes imaginative material
Magical realism – story where magical or unreal elements play a natural part in an otherwise realistic environment
Meta fiction – also known as romantic irony in the context of Romantic works of literature, uses self-reference to draw attention to itself as a work of art, while exposing the "truth" of a story
Mystery – this is fiction dealing with the solution of a crime or the unraveling of secrets
Mythology – legend or traditional narrative, often based in part on historical events, that reveals human behavior and natural phenomena by its symbolism; often pertaining to the actions of the gods
Mythopoeia – fiction in which characters from religious mythology, traditional myths, folklore and/or history are recast into a re-imagined realm created by the author
Picture book – picture storybook is a book with very little words and a lot of pictures, picture stories are usually for little kids
Realistic fiction – story that is true to life
Science fiction – story based on the impact of actual, imagined, or potential science, usually set in the future or on other planets
Short story – fiction of such brevity that it supports no subplots
Suspense/thriller – fiction about harm about to befall a person or group and the attempts made to evade the harm
Tall tale – humorous story with blatant exaggerations, such as swaggering heroes who do the impossible with nonchalance
Western – set in the American Old West frontier and typically set in the late eighteenth to late nineteenth century
SUBGENRES OF GENRE FICTION
Picaresque novel (picaresco)
Science fiction robinsonade
Young adult fiction
Campus murder mystery
Picaresque novel (picaresco)
Contemporary slave narrative
Novel of ideas
Christian science fiction
Contemporary Christian fiction
Epic / high fantasy
Fantasy of manners
Sword and sorcery
Supernatural / paranormal
Cyberpunk derivatives, aka punk
Hard science fiction
Military science fiction
Parallel universe, aka alternative universe
Soft science fiction
Speculative cross-genre fiction
Sword and planet
LGBT pulp fiction
Gay male pulp fiction
Lesbian pulp fiction
Lesbian erotica fiction
Essay – a short literary composition that reflects the author's outlook or point.
Owner's manual (also Instruction manual, User's guide) – an instructional book or booklet that is supplied with consumer products such as vehicles, home appliances, firearms, toys and computer peripherals
Journalism – reporting on news and current events
Lab Report – a report of an experiment
Memoir – factual story that focuses on a significant relationship between the writer and a person, place, or object; reads like a short novel
Narrative nonfiction/personal narrative – factual information about a significant event presented in a format which tells a story
Reference book – such as a dictionary, thesaurus, encyclopedia, almanac, or atlas
Self-help book – information with the intention of instructing readers on solving personal problems.
Speech – public address or discourse
Textbook – authoritative and detailed factual description of a topic.
ADDITIONAL GENRES OF NONFICTION
Contemporary slave narrative
Diaries and journals
Fable, fairy tale, folklore
Philosophy of religion