If there is more publishing in the occult topics right now, does that mean people have a better chance of selling it, or a worse chance? Will we hear there is too much of a topic so editors won't buy it right now? I ask, because I heard that from an agent at a conference several years ago.Observing a trend in the market is like observing a trend in weather systems. How does a storm begin? When will it end?
Most trends are over in two years or less.
Zombies, for instance? Already dead. Trend timetable: 3 months.
Vampires? Still undead. Trend timetable: who knows?
And it's funny (and unpredictable) the way some trends are over before you can point at them and others build, and build, and build, and just when booksellers are rolling their eyes and wondering when it will finally be over, suddenly it gets really big.
People in the industry and outside of it get a great deal of satisfaction in talking about what started a trend (me included), but it's never really that simple—and whether you think it was Bram Stoker or Joss Whedon or Stephenie Meyer who started the vampire trend, not one of them knew when they were working on their vampires that they would be enormously influential.
So in terms of predicting trends: you can't. And in terms of predicting when a trend will be over: you can't.
But generally speaking, since trends are usually over in less than two years, and it usually takes publishers two years to publish a book, chances are that any trend you see in the marketplace right now is, in publishing, already rotting in its grave. With a stake in its heart.