Internet Protocol Security Architecture (IPsec for short) is important. Knowing about it may not be important to you but its existence and development over the years is essential to the increasing acceptance of the Internet as a vehicle for such things as Virtual Private Networks. If you do not already know RFC stands for 'Request for Comment.' I always consider that particularly misleading as it does not indicate that an RFC is much closer to being a rule.
There is nothing in this book that you cannot obtain in electronic form from the Internet. However many of us prefer to have our information in a single bound hardcopy version that we can carry around with us and that does not depend on the batteries in our laptops being charged. If you need to know about IPsec you may consider this book worth the cost. If you are merely curious about the subject, you might prefer to find the electronic versions by visiting a website such ashttp://www.Internaet-Standard.com/