The conventional advice given to authors (by agents and indeed by publishers in that they hate to buy out of that niche) is "If it works DON'T ever leave that niche or even series."
I've often wondered about this. Is it the niche? really? So any other plonker who wrote quest stories with a representitive cast of elves and hobbits and wizards, or a emo sparkly vampires or boy wizards at boarding-school would be a run-away success? Yes, well that kind of thinking does seem prevalent or there would be no trends... to fail. Because they all do. Sooner or later readers explain to agents that no, it's not a ring - quest with a substitute gnarlstone, or emo sparkly vampire with a new home-town that they actually wanted. It was more JRR Tolkein or Stephanie Meyer. Which of course is not what they got... The typical response of the gatekeeper fraternity in response to this is 'there must be a new trend'.
There are trends... but I suspect they are an effect rather than a cause. The cause is a good piece of writing intersecting with reasonable distribution, a good cover and something in the public zeitgeist of the time. And these are not equal in proportion, but all are required to make it work. Of course the proportions are what seperate the sheep from goats. Think about it: Think of your favorite author -- be it David Gemmel or Terry Pratchett -- would you read their work if the wrote outside their niche? (if the answer is yes, then their work's success is not a result of distribution, cover or the zeitgeist. It's no use using them as a 'trendsetter'(if you're an agent or publisher) because that's not why they're popular.) Of course some authors did/do some niches better. Heyer wrote better Regency than detective. But as often as not authors are forced into adopting psuedonyms (which because the distribution/cover/zeitgeist thing is a lottery often fail). Yet readers do follow names.
So: Should writers stick to their narrow lasts? Are trends even worth guessing at?
would you follow your favorites into another genre? I'm thinking about writing a non-fiction foodie/self-sufficiency type book. Would you read it - assuming you enjoy my fiction?