Well, no need to read the book for this simple reason: I’ve read other books about the subject by more balanced authors - he adds little to nothing new.
I watched a lecture from Robert Spencer and I’m pretty sure he takes the dialogue into the wrong direction.
These days: there are think tanks, and lobbys, and publishers constantly producing and reinforcing and reproducing their interests saying nothing new - there have to be a 1000 Robert Spencers (sponsored by whomever) endlessly saying the same…
There are countless authors (many are academics teaching at university) whos “intellectual production” has little to no value…
And this is the main thing: Not a single sign in Robert Spencer’s speeches puts inter-faith dialogue at the forefront as the best solutions (not to mention he “blames Islam” yet forgets the role of politics all together - an all to convenient negligence.)
In alternative, I’d recommend anything written by the : "Pontifical Council for Inter-religious Dialogue"
And what this “Pontifical Council” says -their content and tone- goes in the opposite direction of Robert Spencer (and the good many) an that’s enough, for me.