Like anything else consumers buy, your book is a product. And consumers have expectations when they buy a product.
For example, if I order a pair of sneakers online, I expect a comfortable pair of shoes that I can run, walk long distances, or work out in. If a strappy pair of stiletto heels show up in my mailbox, I will be seriously disappointed. If someone takes me to see a movie and tells me it’s a comedy, I expect there to be humor, for it to make me laugh. If I show up to “said” comedy and there’s a killer on the loose slashing up bodies, I’m going to get up and walk out.
It’s no different with your book. Readers are true consumers. If you’ve written cozy mystery that meets the expectations of the genre, cozy mystery readers will consume every book in the series. If you tell me your book is a cozy mystery and there’s a professional private investigator tracking down a serial killer in a small New England town, you’ve only got the setting right. I can tell you the readers will be downright angry that you aren’t giving them what they expect. Cozy mystery readers expect an everyday-person protagonist like themselves, one who has stumbled across a body in a small town “cozy” setting—like an independent bookshop—and is driven by some personal motivation to find the killer. For this genre, there is always a hook linking future books in the series together, like a bed and breakfast, a bakery, a sewing club. There’s no graphic violence, no bloodshed, no on page sex, and no drugs.
Likewise, romance readers expect the heroine and hero to meet in the first chapter, for the romantic tension to build up to sex—where cheating is taboo—and a happily ever after or a happily for now is a must.
And don’t forget word count. A cozy mystery reader won’t appreciate a 150,000 word story like a fantasy or science fiction reader would.
Although there are always exceptions, whether you’re trying to get an agent or self-publishing, you will likely be more successful if you know what genre you are writing in and if you follow the expectations as closely as possible. Even if you are mashing genres, you need to be able to communicate to agents, editors, and readers what exact elements of those genres you are mashing.
So, how do you get to know your genre better than you know yourself? There’s a wealth of knowledge online regarding genre guidelines. You can go to the bookstore and study the types of books you see in the section your book most closely matches. You can go onto Amazon, pull up books you think are like yours and check the categories assigned, but the best way to know your genre is to read, read, read and take note.