Cory Doctorow writes in Locus magazine on self-publishing and why anyone should care about your work. Drawing on his experience working in bookshops, he talks about the limited shelf life of printed books in days gone by:
But the reality of books was this: a publisher’s rep would come in and tell us breathlessly about the lead titles – how much promotion they were up for, how much the house believed in the title, how well the author had done before. We’d order a pile of hardcovers, generally a smaller pile than we’d been asked to take, and usually, they’d sell modestly well. Then we’d return the leftovers, and some months later, they’d resurface as remainders, with their dustjackets clipped or magic-markered lines drawn on their page-edges. Then they’d come in as paperbacks, hang around for a few months longer, and vanish. Sometimes, a copy or two would surface as used trade-ins, and sometimes a regular would ask us to order a copy, but within a short time, the book would no longer be in the publisher’s catalog in any form. It would be gone.
He says that by and large, not much has changed, even with digital books and the new wave of self-publishing authors, and unlike publishing houses, authors often haven't invested years and millions of dollars trying to crack the successful marketing formula.
It doesn’t really matter how much time you spend hanging around bookstores or browsing online stores, until you’ve marketed a book, you don’t really know how to market a book.
Read the article here. It's a well-written, easy read, though it doesn't really answer any questions. It seems that the journey towards success as a writer is still one best felt out step-by-step: http://www.locusmag.com/Perspectives/2011/09/cory-doctorow-why-should-anyone-care/