A book is one of the few objects that is both itself and its own advertising. A rack of books in a bookshop becomes a billboard for that book. It's as if the book is a pixel in a great poster advertising itself. Music is different. The radio works as publicity there. Big publishers like to sledge a load of books in and it works. The book unit cost for a paperback may be less than a pound sterling and they can easily be trashed after they have served to promote the book ie. returned to the publisher.
This model however doesn't really work with the small publisher. A few books sideways on in a lot of stores advertises nothing. To achieve an advertising function the books must be in a different place- maybe on the till of a health food store if that is appropriate. I think it helps to think of physically selling books -what about getting milkmen to sell books?
The final thought is about vertical integration. In non fiction its easy to ally writing with the subject- offering talks, expertise, tours etc. With fiction it is harder - but there is always a way.
With the rise of kindle there is a corresponding rise in the book as art object. The first 350 copies of any hardback should be lovlingly signed and sold at a premium. All subsequent signed books must be less lavish and clearly differentiated from this collectors model.