What she said.
(And yes, somebody is saying, but Bear, aren't you writing for five different publishers in four different subgenres?)
Yes. I'm publishing science fiction with Bantam Spectra, heroic fantasy (with truepenny) for Tor, urban fantasy/secret history (You know, that Tim Powers subgenre) for Roc, an alternate history collection for Subterranean, and a short fiction collection with Night Shade. (And Sarah and I are peddling a YA historical mystery, but those are just fun to write.)
Charles Stross is another good example of a relatively new (where pro for the last decade is still kinda new, in publishing terms) writer who's doing the same thing (He's got his more-or-less hard SF, his Laundry books, and the Family Trade series going on.) I also know several other writers who are writing two or three subgenres under different names. (y'all could identify yourselves, if you wanted.)
I'm also writing two or three books a year, and I was doing it for long enough before I broke into print that I had a convenient backlog. And I wouldn't be writing for more than one publisher if my publishers weren't each so interested in maintaining a brand.
This is how it worked. Spectra bought the Jenny books, option on the next F or SF novel. The option novel I sent them was B&I. They passed for a complex of reasons, one of them being that Anne-my-wily-editor thought it would be smarter to keep the science fiction coming.
...now, at this point, my contract with Spectra was officially terminated. Neither one of us owed the other a damned thing. And if I were the type to get huffy, I could have stalked off and taken my business elsewhere. All well and good, sure. And we did take B&I elsewhere--to Roc, which bought it.
But instead of the huff, Jenn-my-agent-Jenn and I decided that, well, if they want science fiction we'll give them science fiction. And I wanted to write Carnival anyway, and had finished a hundred pages of that, so we sent that in as a proposal.
...Suddenly, I have two publishers.
A year later, repeat this process with A Companion to Wolves, which was first submitted to Penguin (which publishes both Sarah and me, in its respective corporate persons as Ace and Roc), rejected there, submitted to Spectra, rejected there, and bought by the lovely people at Tor.
...as the previous itinerary post would tend to indicate, I don't currently plan to terminate my relationships with Spectra or Roc unless they invite me to seek publication opportunities elsewhere. So, at this point, I have three mainstream publishers, and two small press publishers. This means I have three different option clauses (none of which can contradict each other), and it also means that my publishers have to be willing to coordinate publication schedules, because it does nobody any good if three eBear novels hit the shelves in the same week. That is what we call a glut on the market.
It's no good.
I think this tale demonstrates several things, though. (1) Persistence is good. (2) Publishers reject books, not authors. (3) Unless that author's a complete pain to work with (4) or her numbers are bad, in which case if you come back with a good book, you can always change your name. (5) It is possible to be quite successful while playing within the rules. (6) I still make what Rachel Vater would consider pretty sucky advances. *g* (7) On the other hand, I'm also getting to build a reputation faster than most new writers do, and that's pretty exciting. (8) No matter how fast you write, you can only publish so many books in a year (9) but if you have more than one publisher, they will most likely each expect a book each year and (10) there's no joy for anybody if you overproduce, and write crap because of it.
Nor is there any joy for anybody if you underproduce, and nobody remembers your first book by the time the second one is out.