I ended up creating two different campaigns on the same budget: one for the Boomer Sisters books, focused on the Champy book and the Pirates book, and one for The Simplicity Cycle.
So far, my advertisements have been posted almost 400,000 times. I've received a total of 255 clicks (94 for the Boomer Sisters books and 161 for the Simplicity Cycle), and used up $48.50 of my $100 credit. So, what's the payout?
Since the Simplicity Cycle is a free download, it's hard to tell exactly what the impact has been there. Lulu tells me it's been downloaded 1328 times, and before starting this campaign, that number was around 1250. So, obviously not everybody who clicks on the ad actually downloads the book, but some of them probably did. So far, nobody's bought the printed copy (not that I expect them to).
As for the Boomer Sisters books, Lulu isn't showing a single sale over this timeframe. Of course, it's possible people have put the book on their wishlist for Christmas or birthday, but none of the 94 clicks have actually ordered the book (yet). That would probably bother me more if I'd actually spent the $48.50, instead of just using the credit.
Still, it's fun to see the number of clicks increase. It's cool to think that people are looking at the books. But once I use up the rest of the credit, I'm probably not going to continue doing this AdWords thing unless there's some correlation between the clicks and actual sales.