You can check it out at amazon here, and the official release date is in April 2015. It’s called Degrees of Freedom: Liberal Political Philosophy and Ideology. I haven’t read it yet (maybe he’ll send me a free copy!), but you can get a flavor of his thinking by starting here (and his bio is here, by the way). His book can also be found on the sidebar.
I’m sure he’ll be adding some more insights into the book here at NOL when he gets a bit more free time on his hands.
EDIT: Updated to mention the official release date.