An Article About the Vampire
One small article can make a lot of difference. This book is called Interview with THE Vampire. Here's the bare-bones plot of the story: A boy is interviewing Louis, a vampire. Why is he called the vampire? After all, he's just a vampire. We, and Louis, meet about a dozen other fanged ones during the course of the novel.
We think the title is simply more dramatic this way. If the book were titled Interview with A Vampire, well, who cares? Well, okay, that would still be something. But still: he's just a vampire. What makes him so special? What would stop us from going out and interviewing another one? Now that we've come to know Louis, though, we doubt any other vampire would be as forthcoming as he is. Those other vampires would probably just eat us.
Oh, by the way, Louis is special, and it's not just about the article. If there's one thing we've learned, it's that Louis is different from the other vampires. Maybe Rice gives him the special spotlight because he actually shows how, ahem, human someone can be in truly inhuman circumstances. Take that, Lestat.