Marketing an ebook via PPC

So, I’ve written an ebook, and am in the process of completing the final copy. I plan on selling it through a website I made, and will take payments via paypal (with an instant download).
I’d like to start a campaign on adsense, adbrite, yahoo, msn, etc. But I’ve also been thinking about getting in on the facebook ad platform, since facebook is so hot right now.
Has anyone promoted digital content through similar means?
Of the people who clicked through from the ads, what percentage ended up buying your product? I’ve heard this number is around 5%, but I’d like to have a real world number so I can bid competitively without losing profit.
I know what the rates are like for adsense and the like. But does facebook have a similar bid rate?
Are there any other PPC networks I should target that have digital media in mind?

See original post by organicCyborg