A key point about writing genre novels (and what ISN’T a genre these days) is to read heavily in the genre you wish to write in.
Which, yes, okay… that’s true. If you want to write Romance, read Romance. Take a look at modern trends, look at how the market is going, then take your story and aim for the biggest readership you can get. That’s all fine.
Here’s the problem: ONLY reading within your genre.
People write from their influences. They can’t help it. No matter how much they aim for originality, you can often tell what their favorite authors are by reading their stories. When their reading is exclusively within their genre, it’s easier to tell what the influences are.
They hit the same beats as the stories they love.
This is why it’s vital to extend your reading list beyond your initial genre passions.
I’m not talking about reading outside fiction itself. I, for instance, love ancient history. If a history goes past the death of the Emperor Marcus Aurelius, I’m usually not interested.
However, history can be very dry. It’s the job of this historian to relate the facts as we currently understand them while acknowledging gaps in the record. A historian can be compelling in relating the facts as we know them, ala Shelby Foote. But there is, of course, a limit to what a historian can do. They are hemmed in by their profession.
If you, like me, are writing Sci-Fi, you have to read within your genre. It’s a must. But you also have to extend beyond the genre to other forms so you can grow your own voice.
Here’s the problem with reading exclusively within your genre: you gain a great knowledge of the genre, but you also pick up all the bad habits.
For instance, in Sci-Fi, the focus is often on plot and world-building. Both are fine, but without fully drawn characters and (more importantly) creating consistent ways that they relate to one another, you get a really neat idea populated by one-dimensional characters. Or worse, you get a bunch of male Mary Sues running around in space and time.
If your Sci-Fi story has some romance, read in the Romance genre. If you want your novel to cross genres to net a larger audience, spread your reading list wide. Read Mystery novels, General Fiction, Romance, Young Adult, etc.
Broaden your knowledge of styles. Discover new ways of approaching your novel by discovering fresh genres, ones that you normally would never read. Go in with the attitude of a student, even if you are learning what you DON’T want to do.
I would suggest finding the top sellers in the genre. Even if their writing is abominable (oh, hi, Dan Brown! I was just talking about you!), you can take a lesson away from it.
Above all, just read broadly. Escape the bad habits of your genre. I think that is the best, quickest way to find a unique voice for your novels.