Regardless of what you write, you do research. The only thing that varies is your research methodology. I didn't consider this consciously until I found myself interviewed by a class of college students. How did this happen? You may well wonder. I know I did.
A teacher I knew assigned his students the task of interviewing people about their jobs. He wanted each of them to go out into the big wide world to interview a research subject. Because his students had no experience with this, he asked me to act as the "sample" interview. This was a scary experience because I don't like to stand up in front of people to talk, but I figured it would be "good" for me.
He brought his class to interview me about being a librarian. He told them to ask background questions of their subjects (in this case me) and to follow leads when they arose - like if I actually said something interesting. He started the ball rolling, then each student raised their hand to ask a question. At first the questions were pretty basic, so I regaled them with tales of the joys of librarianship. Somewhere along the way, I mentioned that I write paranormal romance fiction. They found this interesting. At least no one was snoring, so I was happy. Several students asked me questions about my writing.
As I discussed researching my books, one young lady asked me how you do research for fantasy fiction? Don't you just make it up? In a moment of profound wisdom (or panic) I waxed eloquent about the importance of worldbuilding. After all, worldbuilding is research. You may not pick up a book to research the world you create, but you create that world from the inside out so you know how it works. You must know the physics, how magic works, what it costs, etc. Or if magic is not involved, how does your shapeshifter shift? Does you vamp burn up in the sun or not? All of it is research.
I've found that to figure out how I want my world to work, it helps me to go to other people's worlds. Sometimes I read other people's fiction for little nuggets. US dramatist, Wilson Mizner summed it up well, "If you steal from one author, it’s plagiarism; if you steal from many, it’s research." I find great ideas and tweak them to make them mine.
Then again, wandering through a new age bookstore or the new age section of a big bookstore gives me tons of ideas for writing paranormal. There are aisles of books about using magic, vampires, werewolves and more. I can read a book on folklore from different cultures then twist those stories to my own ends.
I've heard writers say there are no new plots, only new voices. Apply it to worldbuilding. If you want a sweeping cultural conflict in your story, study a past culture for historical conflict then turn it on it's ear. J.K. Rowling did this masterfully (or mistressfully) with the Harry Potter series. The entire time I was reading book seven (no, I'll present no spoilers so relax), I was powerfully reminded of the Nazi regime. She took the universal concept of persecution of "lesser" or "lower class" citizens and made it all her own by labeling them Muggle-borns then built her conflict around it, and she did it brilliantly.
The great thing is ideas are everywhere. It means that research is never finished and a researcher's job is never done, but this doesn't trouble me. For me, research is the fun part!