Before your book has words, it can have a cover

(My first book, published by Doubleday in 1977)

If you write a book that gets published by a traditional publisher, it can take three years to find an agent and for the agent to find a publisher who will accept you and produce the book. In this long process, one of the last things that gets done is cover design. The author may have some input, but the publisher has the final say on the design -- and even on the title of the book -- which can certainly influence the way the cover looks.

• If you are working with a self-publishing company, the time between writing and printing is compressed from years to months, but the cover still comes after the writing.
• But in independent self-publishing (which I do), I've found that it can be very useful to have a cover design even before the first word is written.
  

Above: This preliminary cover was designed a few years ago. I hadn't started writing the book yet. The cover design and the title changed later on as the book evolved.

Above: early and final versions, separated by about two years

You don't have to have a final design (in fact, you shouldn't) but even a "rough layout" will help solidify the project in your mind. The more real the book is to you, the more likely you are to keep typing. If you have front and back covers, and a financial investment in what you've paid your designer to produce, it's natural to want to fill the space between the covers and start selling some books.

• Living with a cover design over a period of months while you write can be very useful. There can be, and should be, an interaction between the exterior and interior of the book. Exterior and interior will evolve together.

The back cover of the book should have a strong indication of what's in the book -- a reason for book-store shoppers to to carry it from the shelf to the cash register and for online shoppers to click to buy. It could be your last opportunity to make a sale, so make it a strong sales pitch!

The back of the book will also be very useful to you while you're writing. It's a summary -- maybe a statement of principles -- that should help to keep you focused and remind you of what you had in mind when you first conceived the book.

• It's normal for the words on the cover to change as you write words for the inside. Sometimes the title may change. Sometimes you just have a "working title" and the final title emerges from deep inside the book. Sometimes you'll come up with a new subtitle, or even swap title and subtitle.

From a strictly business standpoint, having a preliminary title and cover allows you to start promotion to build awareness and desire in advance. If you have an "author's website," your future covers should be shown there, along with brief descriptions and approximate publication dates. If you blog, show your next book(s) on the blog, like I've done. If you're active on Facebook and Twitter, you can display future books there, too.

At the top/left below is the latest version of the former 'Mona Lisa' cover. It has a new title and is now part of a series of books with comic-book style covers.:

 

The books shown below have covers, but nothing inside the covers. The designs and titles will likely change before publication. Maybe some won't get published.