It took more than a year to read this book, this was on purpose because I wanted to think about all the philosophy in it. Oh, and despite the author's prime comments, it has a lot more to do with 'Zen' than he stated. Although the subject is not mentioned as such.
If you want to relax, don't read this book. If you want to challenge your mind, do read it, keep an open but critical mind and take your time.