eihab, hi, the best book to read about TCP/IP, subnetting, and supernetting, is the classic technical TCP/IP book by DOUGLAS COMER, called Internetworking with TCP/IP Vol.1: Principles, Protocols, and Architecture, now in its 4th Edition, which you can buy from
www.amazon.com or any other retail book store site.
His Internetworking book is considered the bible of TCP/IP. His book has been referred to and based on many times over by many network professionals and experts of today since he first wrote it in the mid-1970's. This book is the de facto standard in understanding and applying TCP/IP.
You can find many books on and many links to him. Just type his name in any search engine and voilą. There are too many web links on him. But here are some of the following links I found on him:
http://www.cs.purdue.edu/people/dec
http://www.informit.com/isapi/author...ors/author.asp
Other excellent TCP/IP book authors you can look into are:
(1) Laura Chappell
(2) Buck Graham (TCP/IP)
(3) CISCO PRESS: Cisco Networking Academy Program: First- and Second-Year Interactive Guide