My team at work read this together, to prep for a meeting. Millington lays out a great path for how to start building a community from the ground up, what to track to prove your ROI, and what signals to look for when it's time to change tactics to support your community as it grows.
It's a good starting place. For a long time we've been going on gut feelings to track growth and ROI. Millington's ideas are solid and useful. I recommend this book for people at all levels of community management, I think the advice is useful and practical.