Advertising online?

I’m planning on buying some non-obtrusive ads (like the text ads on K5) to promote my new book, Dancing Barefoot.*
I was reading the “Tip Jar As Revenue Model” story at K5 when I got the idea. I was specifically inspired by this post.
I am terrible at marketing and promotion. I hate advertising, but I know that it’s the best way to let non-WWdN readers know about my book.
Has anyone used advertising online? Does it work? What are some of the pitfalls you’ve encountered that I can avoid?
I’ll leave comments open on this thread for responses directed specifically to these questions, only. I really appreciate any help or direction you guys can give me.
*(thanks to Yoav Rogovin for pointing out my obvious gaffe in leaving out the details of the book!)