What determines whether commercial fiction novel comes out as harcover or trade PB initially

I don't know if this is the right place for this question. If it isn't, please let me know so I can ask a mod to move it.

The "typical" publication pattern one always hears about for commercial fiction that is trade published by a big 5 subsidiary is that it gets a hardcover print run, then after about a year (maybe after longer if it's on the NYT bestseller list or something), they bring it out in a mass market paperback, or maybe a trade paperback. E-books, of course, seem to come out at the same time as the hardcover these days.

But in my own genre (fantasy) many, maybe even most, books never seem to end up in hardcover at all, even when first published by big 5 imprints (Orbit, Daw, Harper/Voyager etc). They come out as trade paperbacks right away (in the old days, many came out immediately as mass market, but this seems to be less common), and e books, maybe going to mass market later.

But some publishers (Tor comes to mind) do bring fantasy novels out in hardcover initially, at least sometimes.

I noticed one agent says on her site that she is actively seeking "lead title" or "hardcover" SF and F. By this, I assume she means books that will appeal particularly to the fantasy/SF imprints that do initial hardcover runs.

So what quality does a book have that makes publishers want to bring it out as a hardcover first, and to believe it has series potential (aside from the writer pitching it as first of a trilogy or a stand-alone novel with series potential). Do agents always shop the publishers that do hardcover runs first, or do some specialize in smaller presses or in big 5 imprints that come out immediately in softcover?

This agent is the only one I've seen so far who specifically mentions that she wants fantasy and SF that will be "lead title or hardcover."

I honestly have no idea what "kind" of story one's fantasy has to be to be flagged by an agent in this way.

Thanks for moving this to the right place

Yeah, so that gets to me wondering how an agent can say, specifically, they're interested in hardcover fantasy and SF. I assume there's some quality this person is looking for in a MS that makes them think it's more likely to attract the interest of editors who hardcover print runs, and I'm assuming that this is because hardcover print runs tend to be more profitable (at least for agents). But I've heard at least one editor (from a big 5 F and SF imprint) say they don't generally have a crystal ball about which of their debut authors will go on to become bestselling authors as opposed to just mid list.

I seem to remember nearly all the SF and F novels I read back in the 80s and 90s were mass market paperbacks, even the ones that had come out recently. Only a few super popular writers had initial hardcover runs back then (writers like McCaffrey and so on), and the only trade pbs I ever saw for SF and F titles were from smaller, more specialized/literary presses (or sometimes special anniversary reprints of books that had been out a long time).

But somewhere around the start of the new millennium, I started seeing a larger portion of the SF and F shelves at the local barnes and nobles and so on given over to new releases that were hardcover or trade paperbacks (and the selection of titles in trade pb form shrank, though there are still some). I don't know if this represents a change in how fantasy and SF are published now (maybe more authors are popular enough to warrant more expensive initial print runs) and how much is a shift in the way bookstores stock and sell books (since their profit margins may be higher on hardcover and trade PBs than on mass market).

Far more of the fantasy books I order from Amazon and B and N online seem to be trade pbs these day, even from big houses.

I'm wondering how ebooks figure into sales also, though that's obviously a separate question.

This person has had a few clients on the NYT bestseller list, so yeah, maybe. Passed on my MS, anyway, so I wondered if there's some sort of characteristic that a fantasy novel must have to make it appeal specifically to houses that do hard cover imprints (and it's something mine is lacking )