I haven't read Pinker's book and currently don't have plan to read it anytime soon. This post is simply to point out three interesting reviews for those who are interested.
First review is by John Gray, a political philosopher formerly at London School of Economics. He argues against Pinker's proposals that the Age of Reason, the Enlightenment, is the reason for the decline of violence. He also questioned Pinker's statement that violence has declined. The review is here.
The second one is by Steve Clarke, an ethicist at Oxford University. He commented on John Gray's review of Pinker, pointing out that Gray has made a case to argue against Pinker's proposal. But he concluded that Gray has not successfully show that violence has not decline. The review is here.
Timothy Snyder, a historian at Yale University, provided the third review. Snyder critiqued Pinker's dismissing the first part of twentieth century global violence and doubted Pinker's collection of "informed guesses" as reliable historical data. He saw Pinker's work as "unscientific". The review is here.