The Definitive Guide is our digital AdWords guide. However, we don't currently recommend it as the latest version came out in 2011. We may be updating it in the near future, so we'll keep you posted on that.
For now, our physical version - The Ultimate Guide - is the most suitable and updated guide to Google Adwords we offer.
And if you're heart's set on having a digital copy, it's available for Kindle on Amazon.com.