(Originally written for IndiesUnlimited as guest post.)

My first book, Avogadro Corp: The Singularity Is Closer Than It Appears, came out in December. It was a great book launch, but after the holidays passed, as you might expect, sales slowed. 
The feedback I was receiving told me the book was good. One friend said she had nightmares after reading it (it’s a techno-thriller). Another reader sought out the coffee shop where several scenes were set and took photos of himself with the book. A local tech blog in Portland posted a very positive review. Amazon reviews are overwhelmingly positive.
So the real question was how to let more people know about Avogadro Corp.
I decided to experiment with Facebook ads. if you haven’t used Facebook ads before, here’s a quick overview:
  • Go to http://facebook.com/ads or click on the advertising link at the bottom of the main Facebook page.
  • Ads consist of an image, a title, a small amount of text, and a destination link.
  • You pay per click, so it only costs you when someone clicks on the advertisement. Ads can be targeted by age, sex, country, region, and interests. 
  • You can set spending limits so you’re in control of how much you spend. You can conduct a useful ad experiment with as little as twenty dollars.
I knew my own writing would appeal to fans of Charles Stross, Cory Doctorow, and William Gibson. I write about similar subjects in a similar style. So I ran a series of Facebook ads specifically targeting fans of each of those authors. 
Here’s a typical ad:

Facebook’s advertising console tells me how much I’m paying per click. For example, in the last seven days, I had 96 clicks on my Charles Stross targeted ad, and paid $0.34 per click.
The advertising console also tells me the CTR (click through rate). For my author-specific ads, the CTR has been 0.2% and higher. That tells me that out of every 1,000 times the ad has been shown, it’s been clicked on 2 times. That might not sound very high, but compared to loosely targeted ads (e.g. people who like read, or people who live in a certain geography), it’s anywhere from 10 to 100 times higher than those more general ads.
The URL for a Facebook ad can be any page on the Internet or even your Facebook author page. I use avogadrocorp.com which is the homepage for my book. I’m specifically trying to drive sales of the book, as opposed to getting people to follow me, or any other objective. You could also send people directly to an Amazon.com page for your book, but I prefer that the URL should in the ad also reflect my book’s brand.
I use statcounter.com to keep track of hits to avogadrocorp.com. I can see who referred visitors to my site, and the overwhelming majority are from Facebook, so I know it’s the ads accounting for most of the traffic.
The tricky part is determining exactly how many books you sell as a result of those visits. The standard industry term for this is conversion. By checking my site traffic through statcounter.com and my book sales through the Kindle Direct Publishing reports daily, over time I’ve found that about my book sales tend to be 10 to 15% of my website traffic. I can’t be sure that all of those sales are generated from my website, but by watching the correlation, I know that most of them are.
Here’s where we have to do a little math.
  1. Since 15% of my website visitors buy a book, then I need to send about 7 (100 / 15 = 7) visitors to my site for each book I want to sell.
  2. Since it costs me $0.20 each time someone clicks on my advertisement, then it costs me $1.40 ($0.20 * 7) in advertising to sell one book.
  3. I normally make about $3.00 on a book, so after advertising expenses, I still clear $1.60 per book.
As you can see the key variables to pay attention to are: cost per click, conversation rate, and profit per book.
If it costs you less in advertising than you make per book: congratulations! You can conduct a successful targeted advertising campaign. Now you can choose to spend more on ads to sell more books, always earning more than you spend.
If your conversion rate is low, you may need to better target your ads to find people who would be interested in the book, or you may need to redesign your website to make buying the book easier, more obvious, or more compelling.

Good luck!