This is a gentle book for readers without a CS background, as the author said in the preface "I work for a computer technology company, but I'm the only computer science degree-holder on my team", Clay has been involved with parallel computation for over twenty years, so he is certainly qualified to write such a book.
My favorite chapters are 2, 3 and 4, as other reviewers commented, this book has a very informal style, something goes like this:
"For those of you who haven't immediately curled up into a fetal position or flopped onto the floor kicking and screaming at the thought of formal proofs of algorithms (and for those of you who did but have now picked the book up again), let me assure you that I consider this a vital part of concurrent algorithm design and it's probably not as bad as you think. The more time you spend creating correct concurrent algorithms from the get-go, the less time you will spend chasing down errors that only show up on those Thursdays when the dates are prime numbers."
But Clay does make his point very clear, so overall I think the book very well serves its purpose.