The Twilight series falls under the genre of young adult, fantasy, and romance, though Meyer categorized her first book, Twilight, as "suspense romance horror comedy". However, she states that she considers her books as "romance more than anything else". The series explores the unorthodox romance between human Bella and vampire Edward, as well as the love triangle between Bella, Edward, and Jacob, a werewolf. The books avoid delving into provocative sex, drugs, and harsh swearing because, according to Meyer, "I don't think teens need to read about gratuitous sex."
The books are written in first-person narrative, primarily through Bella's eyes with the epilogue of the third book and a part of the fourth book being from Jacob's point of view. When asked about the structure of the novel, Meyer described her difficulty to pinpoint the premise of the novels to any specific category:
I have a hard time with that. Because if I say to someone, 'You know, it's about vampires,' then immediately they have this mental image of what the book is like. And it's so not like the other vampire books out there–Anne Rice's and the few that I've read. It isn't that kind of dark and dreary and blood-thirsty world. Then when you say, 'It's set in high school,' a lot of people immediately put it in another pool. It's easy to pigeonhole with different descriptions.
The books are based on the vampire myth, but Twilight vampires differ in a number of particulars from the general vampire lore. For instance, Twilight vampires have strong piercing teeth rather than fangs; they glitter in sunlight rather than burn; and they can drink both animal blood as well as human blood. Meyer comments that her vampire mythology differs from that of other authors because she wasn't informed about the canon vampires, saying,
It wasn't until I knew that Twilight would be published that I began to think about whether my vampires were too much the same or too much different from the others. Of course, I was far too invested in my characters at that point to be making changes... so I didn't cut out fangs and coffins and so forth as a way to distinguish my vampires; that's just how they came to me.