Value for Price
Google Cash has been around for years and was once labeled as the "bible" to earning money with Google Adwords. Things have changed over the past few years and the product has been replaced by some of the newer books offering more up to date techniques, strategies and superior quality in the way of layout and design.
Google Cash is still highly recommended as it focuses on Google Adwords, however the techniques are offered in all previous mentioned books. Google Cash lacks many of the bonus techniques that are offered in the other top rated e-book Beating Adwords which is one reason why it is ranked lower. Overall, Google Cash is a great book, and has a proven track record to support this claim.