I putz about on Reddit sometimes, and ran across this question in /r/Writing (relevant bit quoted below):
[I’ve written some short stories now.] I was wondering whether I should submit somewhere online, or put like 5 shorts together and submit it as a book.
I think this cannot be repeated enough times to new authors:
Always attempt to sell short stories, poems, and flash fiction to periodical and anthology markets first.
The reasons are pretty simple.
First, unless you are already a Name – and let’s face it, if you’ve got this problem, you’re probably not – it’s very unlikely that a publisher is going to take a risk on publishing a collection of your work. They might – hell, I have – but that’s by and far the exception, not the rule.
Their reason is the same one that it’s not worth your time to start by publishing a collection on your own, either.
My experience has been that people buy short story collections of authors they know – either from reading them, or because they’ve met them at a convention or signing. If you don’t already have that base working for you, it’s a hard sell to both publishers and readers.
Second, it’s that pesky "First Publication Rights" thing. Most collections – like my Kicking The Habit – are mostly or completely made up of reprints. This is reasonable – to get all the stories in Kicking you’d have to buy quite a few books and magazines, some of which you’re not going to be able to find any longer. Publishers also recognize this, so if you were to sell a collection to a publisher, they wouldn’t expect most (or any) of the stories to still have their first publication rights.
Magazines and periodicals and anthologies? That’s a different story. They do want previously unpublished works – and even if they’ll take reprints, the rate is usually far lower.
Third, by selling to other markets, you’re reaching new audiences. And that is always a good thing.
So again:
Always attempt to sell short stories, poems, and flash fiction to periodical and anthology markets first.
There’s plenty of places to look for where to submit: check out The Submissions Grinder, Ralan.Com, duotrope.com, or even things like this open subs thread on Reddit.
There’s new markets popping up all the time – for example, submissions for recompose will be opening up after the Kickstarter ends Tuesday night. (You still have time to back recompose! Exclusive content starts with a pledge of as little as $3! Don’t wait!)
So even if you think you’ve "done the rounds", set the work to the side for a little bit, re-read it to see if you’re still happy with it, then start again.
It’s worth it.