Every genre has its own set of conventions, which provide readers with a sense of continuity between books within a genre.
- You have to introduce the villain before the climax in a mystery novel.
- You have to provide rules (i.e. limitations) for magic in a fantasy novel.
- You have to provide negative consequences and limitations for advanced technologies or systems in a science fiction novel.
- You have to delve into the character(s) in a literary novel.
Thrillers, chick lit, romance, westerns, horror…they all have their own conventions.
When writing in a particular genre, you have to be familiar with those conventions. That does not, however, mean you have to follow them. If you break a rule, because you know that rule, because you intend to break that rule, and because you have a purpose for breaking that rule, then go ahead and break it—but break it well.
Just don’t break genre conventions out of ignorance. That’s disrespectful to your readers.
Of course, in order to know genre conventions—in order to understand the conventions, their strengths and weaknesses, and which ones to break, when and why—you have to read novels in that genre. A lot of them! Respect the audience you’re writing for enough to read some of what they’ve read and loved. If you can’t do that, then you really shouldn’t be writing in that genre. If you love those novels too, well that’s even better.