Andrew Wheeler is my favorite writer when it comes to the practical minutiae of everyday publishing and bookselling. He explains things clearly, thoroughly, and often with a good sense of humor. His perspective is that of someone who does marketing for a living (he's a science fiction fan who markets business books these days), and he is more practical in his approach than many of us who just wish every corner had an independent bookstore stocked with all the sorts of books we like.
His recent post on why some books get stocked by chain stores and some don't is one of his best yet, and it moves through all sorts of different subjects having to do with publishing. Idealists will be annoyed, but before changing the world, it's important to know what the state of the actual world is.
I considered excerpting a paragraph and posting it, but that might prevent people from reading the whole thing.