I used to be of the opinion that it wasn't rocket science (I've talked to Iron Man about rocket science, so I know). After I wrote a few books and researched a lot, I realised that it can be kind of hard.
I've noted down some typical genres, a rough idea of what they entail, and some published books that fit in them. Yes, I've done the research. I am Bruce Banner after all.
(Note: This isn't an exhaustive list of genres. And I'm only talking about Young Adult books, because this is after all YAvengers.)
epic or high fantasy
Think: swords, castles, knights, quests and smelly peasants.
Think: contemporary setting with supernatural happenings (also set in a city).
Think: modern day setting, usually includes school life and romance.
Think: speculative future, with perfect government that's secretly corrupt.
Think: futuristic speculation that explores the beginning of world corruption (floods, fires, wars, earthquakes).
Think: werewolves, vampires, fairies, romance between humans and supernatural creatures.
Think: true to history but with made-up characters.
Think: steam and inventions (clocks and gadgets) probably set in the 1800s or early 1900s. Alternate history.
Think: out of space, with planets and exploration, cool technology.
Think: any setting, but probably modern, with horrific and creepy events.
Think: any setting, but the characters must survive against nature.
What genre is your current work-in-progress? Share in the comments!