Caveat: I have met and like one of the authors, so I am biased.
I enjoyed this book, though I worry time will treat it poorly, as it has already been victimized by the authors’ success. This book is basically a description of how the authors (and others) created google ngrams. It’s not just technical stuff either – it’s a lot of their philosophy of what they find interesting.
The problem is that a lot of the book consists of interesting patterns and correlation they found using ngrams. The correlations are neat, but given how popular ngrams has gotten (and especially its spike in popularity a few years ago, the examples don’t feel as exciting as they must’ve when the book first came out. This isn’t exactly a knock against the book, but it does make some large sections of it less interesting than they might’ve been.