I wish there were a central location where agents and editors could post what they've been seeing too much of. If there's a run on drug books/mysteries where Jesus's clone did it/fantasies where farm boys get blipped through portals in search of magical jewels, it would be great to know about it. It would also be entertaining, because so few of the topics agents complain about are obvious to those of us who don't see the slush.
It would be cool, but it would be for amusement purposes only.
All of you unpublished writers out there, here's a message from me: Don't follow a trend or even ignore a trend. Don't think about trends. Just write the novel you've always wanted to write. Then when that gets rejected, write the novel it turns out you really wanted to write. Rinse, repeat unti; you actually get published, and then say, "Thank G-d that original novel didn't get published! That was crap."
I'll turn this into a larger discussion of trends. In this case I'll be using The Da Vinci Code, not because I have some obsession with it but because it's really the most massive example I could use, as opposed to all the little ones you might not have heard about.
When I was in college (fall 1999- spring 2003), there was a huge trend on an academia level of studying early Christianity - the gospels themselves and the people who wrote them (the gospel was probably written over 20 years after Jesus died), and the generation or two that followed immediately afterwards. There a bunch of feminist professors who were interested in women in the early church and writing about the role of women and how Paul was against women taking leadership roles in the church. The early Celtic Church, where women could be priests, had also been a hot academic topic for several years. People were publishing their materials on university presses, which is what professors do, and they would immediately go out of print, which is what happens unless there's some real non-academia interest in the topic. (Also, a lot of professors can only write papers, and their books are just long papers. This is one of the many reasons I didn't go for a PhD in history)
I have a sneaking suspicion that Dan Brown got some of his ideas from this particular academic trend, and then was inspired to make it a series of novels about early Christianity, and one of them was The Da Vinci Code, and as we all know, it became the biggest non-Harry Potter publishing phenomenon in decades. This lead to the knock-offs and academic books that followed, both of which I will discuss.
(1) The fiction knock-offs of The Da Vinci Code were not written, for the most part, by first-time writers. They were written by established writers - part of some agent's or publishing house's "stable" - who were either inspired by the success (and saw little dollar signs in their eyelids) or told by the publishing company to go "write a book about that." Generally the negotiations go like this:
Publishing House: "Do you want to write a The Da Vinci Code knock-off?"
Established Author: "How much will you pay?"
Publishing House: "A lot."
Established Author: "When do you want it? Friday's bad for me."
There are also book packaging companies, which you've never heard of because they don't advertise to the public, who are put in charge of packaging a novel that resembles whatever the publishing house wants it to resemble. They'll get some writers to work with them and do that. It's all in-house.
(2) History books that deal with the same (or similar) subject that said novel discusses. These books are the type that appear in the bargain bin at Barnes and Noble. They're not original. Chances are they're a republished version of some academic text on the subject that was published by a university press in 1971 and went out of print in 1972 and now is impossible to get. Barnes and Noble's publishing house (same name) bought the rights, which were quickly sold because the author realized their book would never see the light of day again otherwise, and then repackaged and republished the book.
The other option is that a publishing house wants to put out a history book that is accessible enough for people to read about the trendy topic, so they approach some established historical author or professor in that field of research and say, "Hey, do you want to write a book?" Then they get the book packaging company in to make sure it's readable (Remember: Most history professors can't write) and put it out as quickly as possible.
And that's where books come from.