I just finished reading "The New Influencers" by Paul Gillin.
The book is best summarized by Seth Godin's quote on the cover: "This is essential reading for anyone who missed the blogging train when it left the station." The book gave a good overview of the market dynamics, current state, and principles of blogging. I enjoyed the case studies, examples, statistics and stories. I'd suggest this book for any manager or senior executive who doesn't "get" social media. It is probably too basic for those in this space, but the stories and statistics are helpful references.