This book is an awesome compilation and collection of the most important networking concepts that would be required to be put in your head for appearing for the CCNA exams. The writing style is extremely simple. The most difficult concepts are explained in an easy to comprehensible manner. The fun is the subnetting. Todd challenges after reading the Subnetting chapter and doing the written tests at the end of the chapter, you will be able to subnet in your head and that you will never forget to subnet if you practice regulary (visa-a-vis being fit to go to the gym). So, if you are looking to buy this don't think twice. Just get it.