Hmmm, I'd start you off with Ken Evoy's now free
"Make Your Site Sell" ebook and then on to some great real books like Jay Abrahams "Getting Everything You Can Out of All You've Got" or just about anything from Dan Kennedy.
Take a look on Amazon and you'll find most of their books in the $10 - $15 range and a search on marketing will turn up other good resources too.