If you want to learn about Modern Control Systems the first time around then use a book written by Ogata, Kuo or Nise. These three authors have some of the best books on this subject that you will ever see.
As for this book
GOOD:
The Matlab part of the book I would give 4 stars. It is pretty good and lets you get acquainted with the control toolbox. There are a wide variety of problems in the book and it has a lot of design problems for the reader. Problems include exercise problems, regular problems (beats me why he didn't put them together), advance problems and Matlab Problems. If you already know the subject then it could possibly be a good design book.
BAD:
Worst book I have ever read. This book offers some of the worst explanations I have ever seen in a book. It is nearly impossible to do the problems with the information given to you. Reading the book is like solving an exercise problem in itself. A lot of times the math is skipped so you have no idea how he got to the answer. While other books happened to spend 4 pages on a topic, Dorf managed to compress it into a useless paragraph. Also, Dorf expects you to clairvoyantly know what a definition is. When reading through a chapter he talks about something without telling you what it is. Somehow he expected you to know that at the end of the chapter, AFTER you've read everything he'll give you a definition list. Very few exercise problems have answers to them so if you are doing something wrong then you will not know. If you are looking for self-study from this book then start crying now because you will throw over 100 bucks in the garbage.
The most definitively annoying thing about the book is how it references other books. Dorf commonly gives you a sentence on a topic and then references the sentence to another book. Those sentences are meaningless and explain nothing, which gave me the impression that I was supposed to go to one of the hundreds of referenced books to learn what he was talking about.
IN SUM:
The only people who will like this book are the ones who already know the subject. I found that after I read Modern Control Engineering by Ogata and understood the subject, I appreciated a FEW of the examples Dorf gave, even though I could find a slew of books that could cover that material better. If you are a teacher looking to make this your class's book, reconsider because your students will not learn the subject.