An excellent article at Slate Magazine by Robert Pinsky. Frequently asked questions about the business of verse.
For writers or anyone interested in how 8 out of 10 readers being female has affected publishing...here is another excellent article.
and interview with literary agent Nat Sobel, who "discovered" Richard Russo and James Ellroy.
But for first fiction, which is really the future generations of writers, it has become a real problem for publishers because they don't have the large list of independent booksellers that they can appeal to. I forget what the percentage of sales is today from the independents, but it goes down every year. I think that's affecting first fiction, particularly short story collections. I love the short story. I love the form. But who's going to take on a short story collection today? Damn few. I think that's influencing the market—the market is feeding on itself.