I used this book as a primary study source for the Active Directory Exam and found it to be limited in many respects. While it does cover most of the required topics, it can be very light on substance in parts, and leave you bored to tears in other sections. Obviously it was written by a collection of authors and hence there is no real coherence to the book. However that said it is from Microsoft, hence authoritative, and does at least touch on the relevant areas. I would suggest using the resource kit to fill in the gaps, or Alistair G. Lowe-Norris book for better presentation or the subject.