The book is very well written and is one of those "technical" books that you can read without getting tired or bored. Not just for professionals, but for anyone who would like to make his site more attractive. Also interesting for non-drupal sites. It is worth buying.
I bought this to learn how to plan and build Drupal websites. It is a very comprehensive book that can be used by both beginners and more experienced users. It covers many relevant issues and I know that I will be dipping in and out for a long time.