One interesting thing about this thread is that nobody has mentioned the most basic thing of all... You have to write a good book in the first place. Perhaps that was in the post that Dr Drib removed. (Not a personal comment, David - I tried to download your excerpt this morning but got timed out - I'll have another go later.)
It's pretty important, though. A good book pushes the marketing forward on oiled wheels. A bad one fights back. Writing good books is what we're supposed to be doing, isn't it?