Hotwired,
Your site looks really good
See, I'm not an affiliate specialist. I manage to make a good living online by promoting online dating services but I don't think dating and lawn mowing have much in common; although... naah, not really
ClickBank seems to be the best option for promoting e-books. I can't really help you here, since I know the business from the publisher's point of view rather than advertiser's.
On the other hand... have you thought of actually promoting other stuff on your website (apart from your e-book)? What do you do to promote your website out there? Do you monitor your traffic? Where do your visitors come from?
Katharina