Dear Miss Snark,
I'm beginning the process of finding a publisher for a collection of literary short stories (the stories are unified by a theme). Four of the stories have been published in literary journals.
The collection includes a novella, and a small journal has expressed interest in publishing the novella serially. Do you have a sense of whether the small publishers that might be interested in my book would be put off if most of the stories, and particularly the novella, had already been published in little mags, or is this always a case of the more the better?
More isn't always better, but pub credits are good. What you'll need though is some new work in the collection so you can say "these are published; this is new". Almost every collection has some bits of new work unless it's a collection by an well-established author.