What is the best book to start learning ethical hacking ?
For stack overflowing (used by many a hack), Smashing the Stack for Fun and Profit is the definitive guide for how this works, and how to protect against it.
I also found Hacking Exposed to be a particularly good book, but it is focused primarily on network security.
Any of the study guides for the Certified Ethical Hacker (CEH) Certification
You obviously intend "hacking" to mean "obtaining access to protected computers and resources without permission", which I find hard to dub "ethical". Hacking as a general (non media-polluted) term simply means playing around with or digging into the internals of something. (i.e. "I've been hacking away at this program for several hours now.") Please be aware of the difference.
As far as learning "ethical hacking" goes I recommend picking up books on securing systems, not breaking into them. Often times they will cover the same material, but from a more "ethical" perspective (Protecting data rather than stealing it.)
The book Gray Hat Hacking is a nice read. If you're a real starter, Happy Hacker is also nice (though a bit old).
Furthermore, the phrack online magazine is awesome for more specific and advanced stuff.
Read Stealing the Network series by Syngress Publishing. It's a collection of stories, while fictional, the techniques, methods and software used in them is very real. It's an entertaining read, places you in the state of mind of the hacker.
First, an ethical hacker is often called a penetration tester, so you may have better luck using that term.
Next, there are a lot of good books on the subject.
- The Unofficial Guide to Ethical Hacking (it's a bit dated, but has a lot of good background material)
- Hacking: The Art of Exploitation
- Gray Hat Hacking: The Ethical Hacker's Handbook
Finally, another related field you might be interested in is computer forensics.
Hacking: The Art of Exploitation --- This is my favorite till now. Any other similar kind of books?