If you believe that placing your book on major web retailing sites will permit it to be discovered and let you live comfortably, then don't buy Jeffrey Marks' "Intent to Sell: Marketing the Genre Novel." If you believe that you will reach a much wider audience if you work as persistently at the publicity craft as the art and craft of writing, than you may not need any other book than "Intent to Sell." The table of contents is organized well enough that you can skip around, though I recommend a cover-to-cover read.
Marks does not say "you need a press kit" or "book signings can be good for you." He says exactly what needs to be in the kit and why you need an 8x10 photo instead of a snapshot, or why your bio should deal almost solely with your writing or aspects of your life that relate directly to it. He advises you on who makes decisions in book stores and how this varies with the size of the business. His discussion of the role of social media is helpful, and it puts in perspective that its use is generally only a very small part of a successful book publicity effort.
The most helpful chapter for me was "Us versus Them," a thoughtful discussion of the different ways to use a public relations professional and how much to expect to pay for varied services. The second was that on "Finding Your Niche," which I would describe as integrating the promotion of your novel among your existing networks without becoming a self-proclaiming pain. Overall, the best aspect of "Intent to Sell" was how to organize your publicity work so an author uses time efficiently.
Marks initially talked in terms of working with your publisher and I was not sure the book would be relevant to self-published writers. He broadens to self-publishing, and both frameworks are useful. Marks writes mysteries, so some of his examples may be more relevant to those who write in the same genre. However, I think the only error in this book is in the title -- you don't need to write genre fiction to learn from "Intent to Sell."
Writing is as much a gift as reading, and you need never sell your work. If you want to do so, buy "Intent to Sell: Marketing the Genre Novel." Now.