Junk
This book is basically a word for word copy from freely avaliable online documents and other books. The author fails to mention the documents that he uses as sources for his factual information. The worst part is, some of the sources the author used were unreliable themselves. Talking about libnet like it is a program just shows how inexperienced the author is in the subject he is writing about. How could one possibly write a technical book about something they don't know much about. As for the ethical part, there is hardly anything ethical about breaking into other systems. If you want to know how the hackers really get in, get hacking exposed. Hacking Exposed pulls no punches on describing how it is actually done. Spend your money on better things.