This is probably a silly question (and I'm sure you can guess my answer). But no matter how much evidence there is to the contrary, there are still writers out there who don't think they need to market.
Before I get into specifics, let me start by saying there is a difference between "I'm not going to market my book" and "I'm done marketing my book". The former suggests a clueless author while the latter can be the result of a lot of different things. You may be out of resources, you might have a new project it's time to promote, or you may have decided that despite your best efforts this book isn't going to happen and it's time to move on.
Those are all perfectly acceptable reasons to stop actively promoting your work. Of course, you're still going to have it listed on your site and reference it in your posts on occasion, right?
I hear lots of reasons why authors choose not to market their work, but here are the top three I've seen recently and why they are lame excuses we all need to get over.
I don't have time to market
Marketing your book will require two commodities from you: Time and Money. They are an indirect correlation to each other (Oooh, math terms). The more time you devote, the less money you need to spend and vice versa. If you aren't willing to put in the time, you need to be prepared to fork over the bucks needed to have someone else do it for you.
If you can't pay someone else, then you absolutely must make the time. No excuses. And honestly, while the behind the scenes work of marketing your book can be tedious it isn't the time suck that most of us think it is.
To test this theory, I went on a book review hunt for a client this weekend. I was specifically looking for bloggers that specialize in reviewing YA speculative fiction. To make the search even harder, I limited my results to those bloggers who accept indie published novels. Despite the constant lamenting that no good reviewers will even look at a self-published work, I was able to put together a list of 70+ reviewers in just over an hour.
Now, more time will be needed to narrow down the list (you probably wouldn't send review requests to 70 reviewers), verify submission requirements, and send out requests. We're probably talking about another couple of hours of work here. It will be tedious, require multiple spreadsheets and probably a lot of coffee, but in about 3 or 4 hours you could send out a large number of review requests to get your book much needed publicity. Split up over a few days, you could have a schedule for tons of exposure in less than a week.
*If even this feels like it's outside your schedule, consider pairing up with another author in your genre with a release around the same time as yours. You can split up the work of researching reviewers and get the work done in half the time.
I don't know how to market
This might have been an okay excuse back in 1994, but it doesn't fly today. My favorite thing about the writing community is everyone's willingness to share their knowledge. Tons of authors have opened their books to talk about what worked and what didn't work. With a little bit of time and efforts, you can find all the answers you need. And if you can't find something, a quick shout for help on Twitter will often yield exactly what you need.
But don't limit yourself to authors. There are so many great individuals out there blogging about small business marketing. Even if you have a traditional publishing deal, you should still try to think about your books from a business standpoint. Some marketing knowledge is universal, no matter what you are selling. I suggest adding a few of these gurus to your regular blog roll and engage in some free education.
Need a place to start? Try taking a look at Danny from Firepole Marketing and Marisa at Live Your Message.
I shouldn't have to market
This excuse is born out of some strange idea that if your book is any good, you don't need to market. Readers will flock to you because of the quality of your work. I'm here to tell you this idea stinks worse than a two-week-old sippy cup of chocolate milk lost under my bed.
You might be the next Suzanne Collins, but if readers don't know you exist, they can't flock to you. Not marketing your book is like holding a garage sale at the end of a cul-de-sac without putting a sign on the street corner. You might have the best prices in town and a lost Van Gogh hidden behind a paint-by-number of a unicorn. It doesn't matter, because no one knows you're there.
Yes, you are a writer, and your primary job is to write. And if you could care less about sales, making money or reaching your readers, then, by all means, refuse to lower yourself to the world of writers who market. But don't be surprised when gobs of glowing reviews aren't showing up and Newbery doesn't call.
Get over it
Marketing isn't easy. It can make us awkward and self-conscious, because we aren't already awkward enough. That's tough cookies. Take some comfort that no one wants to spend multiple hours each week on marketing. We'd all rather be writing (or watching cat videos on YouTube). But we do it, because in order for our words to mean something to a reader, they have to know the words exist.