I just finished reading this book. I found the general concepts to be good and reinforces the need to build a network. Some very close parallels to Mark's reccomendations for building a network.
What I didn't like about the book was how over the top some of his tips seemed to be. All of his examples on the value of networking were from his later days after he had build his huge network. Networking with top CEO's and the like is a great tale, but what is missing is how I can go from where I am now (mostly network contacts in my company) to a broader network. All that detail is missing. Also Keith has a great advantage of running a business or consulting, giving him an advantage in meeting a lot of people.
It would be great to have more practical advice for building a good network for people who don't have contact with customers (engineers, IT staff, Customer Support reps). It seems all the great advice on networking will work best if you are in consulting or sales.
Overall a good read that provides some useful tips and reinforces the importance of building your network.