We are currently using this book as a text in school. The book is more like an overview (hence the title) but it's so over the entire view that it's hard to get any real substance out of it. I'd rather have just read a glossary that told me what VPNs, DMZs, firewalls and encryption are. The mispellings and other typos are enough to make me want to throw this book out of the window. Did the editor actually proofread this thing? This is an alright reference as an addition to another book but it fails to stand on it's own as a text. Big disappointment.