Do not write to chase the current market, writers are advised, because today's trend won't be there tomorrow and you'll be left with a manuscript that can't be sold.
What you want to do is what J. K. Rowling did with her Harry Potter series: be the trendsetter and set the style. Then close up shop when it's clear that you've ridden your trend to the end of its natural life span.
Look at what has happened to Billabong, the Australian surf apparel firm that is, at this moment, all but dead. Only a few years ago it was at the top of its trend, its clothing line highly desirable by those who wanted to appear surf-ly.
Like an author hitting the market at the right time with something different, Gordon Merchant developed a product that resonated with a market segment flush with cash and willing to buy. Back in the 1970's, youth culture was going strong and the surfing scene had a certain cachet, especially among those landlocked youth who could only dream of riding the waves. But they could dress the part, if they bought Billabong apparel.
Mr. Merchant rose in the ranks of the world's richest, selling board shorts and hats, outdoor gear and whatever else the public would buy with his logo emblazoned on it.
Like any normal human being, Mr. Merchant wanted to enjoy what he had earned, and so he stepped down from the daily operation. Now, if he had imitated J. K. Rowling, he would have started up some other firm in a related field, perhaps a clothing range aimed at Australian hip-hop aficionados. He might have given birth to a new trend.
Instead, he pulled back and let his empire be run by others who decided that what was needed to expand market share was a large collection of shops in which young trendsetters could browse the offerings. Tricking out those emporia required cash, and cash came from debt financing because wasn't that the rage a few years back?
Imitators came along and took some of Billabong's market share, imitators with less debt to services. And the Australian surfer culture began to fade into obscurity as well, with some other new fashion stylings becoming popular with a fickle crowd looking for variety.
Billabong is valued at approximately zero. The trend came, and it went, while the executives who ran the place thought the trend would last forever. They didn't bring in someone to introduce the next big thing, the craze of the near future.
So it won't do you any good to write about a boy, or a girl, wizard, no matter how perfect your prose. Write what you know, or what you feel passionate about, and maybe you'll get your manuscript into the right hands at the right time, like Billabong's surfer styles arrived in a timely manner. Then you can worry about staying on the top of the wave instead of being washed under.