The top Inbound Marketing Book is, of course, "Inbound Marketing" by Dharmesh Shah and Brian Halligan. The book is based off of all of our experience doing inbound marketing at HubSpot. I highly recommend you spend the $17 to buy it on Amazon.com.
World Wide Rave is an awesome book for three reasons:
1) It is very timely since creating a World Wide Rave is part of the new trend of inbound marketing
2) The book uses some great examples of smalll businesses and entreprenerus creating thier own World Wide Rave
3) It is very easy to read and approachable, so you don't need to be a viral marketing expert to learn something from the book