Happy to. This is coming straight from my experience, so another agent, or an editor at a particular house, may be seeing different trends. My thoughts...
--The continued growth of romance -- particularly historical romance. Let's face it, last year the publisher who saw the biggest growth was Harlequin, and they did it in a down year for most publishers. The fact is clear: readers in a bad economy like to escape by reading romance novels. You can roll your eyes if you want to, but it's the truth. (And yes, I'm happy to say I represent some excellent romance novelists.)
--Thrillers aren't selling like they used to. They're far from dead, but the whole CIA/24/CSI thing has been fading. James Patterson and other bestselling novelists can still move large quantities, but once you move away from the bestselling authors, it's much slower (and, frankly, much harder to place a new novelist).
--There is a renewed interest in Americana, particularly during sunnier days. We're seeing interest in the Victorian and Edwardian periods, for example (um... assuming it's fair to use British terms for American history). That seems to be a trend away from seeing so many wartime sagas -- perhaps a reflection on our fatigue with the never-ending war in Iraq.
--We've seen a lot of growth with fiction that surrounds historical events. Not a retelling of the events, but of stories that touch on history. So, for example, we're not seeing novels that re-tell the assassination of President Lincoln, but we ARE seeing novels that have to do with people who were in the vicinity, or who knew John Wilkes Booth, or who were at Ford's Theater, or who were part of the chase to catch the conspirators, etc. Again, not so much focused on the event itself, but on characters who were influenced by the event.
--Literary fiction is definitely a growth category in American publishing. Take a look at any bestseller list, and you'll see a lot of literary fiction. Not only that, but many of the books have a clear spiritual thread -- something I don't see many people recognizing or reporting on.
--One of the most-reported growth trends has been in paranormal fiction. And while we see a lot of YA titles (Stephanie Meyer et al), much of the growth in adult paranormal novels has been of the "erotic" stripe.
--If you separate paranormal from fantasy & speculative fiction... well, for all the talk about the huge growth we're going to see in fantasy titles, I'm still not seeing publishers buy or sell much spec fiction. I know that pains all the fantasy writers, but the fact is it's still a fairly narrow niche. Speculative readers are devoted, and there are more than there used to be, but overall the industry isn't viewing this as the next big thing.
--I see mixed signals in the horror category. Some think it's up; others think it has run its course. I don't have a firm opinion one way or the other.
--Of course there has been huge growth in the Christian/inspirational category over the past 7 or 8 years. The incredible growth has slowed, making some think religious fiction is hurting, but that's just not true. Christian fiction is still a HUGE category, and there is still growing interest from those houses who were late to jump on board during the heyday. So while, yes, we're not seeing the big growth in titles that we did a couple years ago, compare the number of titles and the number of genres and sub-genres to what we saw just three years ago.
--One of the most visible areas of growth in the inspirational category has been Amish fiction (or "bonnet novels"). Some people have said that it's going to fade out, but I don't believe it. I think it has established itself as its own sub-genre. What Bev Lewis started and Cindy Woodsmall followed has turned into its own category of fiction. That sort of thing happens sometimes -- consider Louis L'Amour creating the giant interest in westerns, or Edgar Allan Poe basically establishing horror fiction. People are still buying it, so it has clearly found its audience.
--A trend among CBA houses seems to be a pulling back -- moving away from some of the edgy themes in order to focus on the safer, tried-and-true CBA story. This is possibly due to the economy and our desire for security and simpler times, or it could be the normal ebb-and-flow of publishing interests among readers.
--And a very strong trend is the growth of small presses, including those who only provide e-book versions of novels. Publishing is going through a huge transition, and with change comes new opportunity. Some new, smaller houses can be more nimble, and they are rushing to create books that are aimed at the new technology. Some of them will survive, some will no doubt see great success and become large corporations (that are perhaps no longer as nimble), and some won't make it through next month. At the same time, we're seeing large publishing houses make a commitment to the new technologies -- even if it may not be as quick or as complete as some writers would like. But the sprouting up of new companies is a good thing for writers.
--And any discussion of trends wouldn't be complete without mentioning the growth of e-books and the shifting desires of readers to see books in other formats. I don't think ink-and-paper books are going away any time soon -- most every reader still loves printed books. But I've got three kids in their 20's, and all of them are comfortable reading a book on a screen -- even an iPhone screen. That tells me when their generation is in charge, the e-book will be a core business, not a side business. It will be a major part of every publishing decision, not simply a sub-rights discussion.
By the way, I'm teaching a seminar in Atlanta next weekend entitled WRITING BESTSELLING FICTION. My co-teacher is bestselling author Susan May Warren, and we're going to be exploring how an author can move beyond just writing another novel, and create a book that has all the qualities of a bestseller. We'll be talking about plotting, characters, structure, themes, dialogue, scenes, and the importance of things like the hero's journey and the inciting incident. We will have some specific time devoted to writing romances and suspense novels, and Susan has some great things to share about finding your writing voice. We'll close by talking about selling your book, creating a proposal and query letter, and we'll offer some face time so each participant can talk about their manuscript. We're meeting at the Embassy Suites in Atlanta, and as I noted the other day, I think there is space for two more, so if you'd like to join us, check it out at www.themasterseminars.com.