First of all, reading this book made me wish I could have been in attendance at the event for which it is the basis. Imagine hearing Charles Taylor, Cornel West, Jurgen Habermas and Judith Butler all lecture on the same day and then discuss back and forth.
Second, the book's brevity is its strength. It helps if you have read these philosophers outside of this book, but even if you haven't, you receive a rather robust introduction to their ideas and their style.
Third, Craig Calhoun does an outstanding job in the afterword of summarizing the arguments. After reading the lectures and debates, and then reading his summary, I have a much clearer view of what religion and its voice looks like in the public sphere. It's really a great little resource.