Book on Chess Defence

In your opinion, what's the best book out there in terms of teaching chess defence for intermediate players?

I believe defense is synonymous with understanding pawn structures, as most intermediate players (me included) often suffer from one of the following pawn maladies to fudge up our position => giving our opponent a weakness to attack.

- play incorrect pawn break moves.
- push pawns in front of our king rationalizing that it is still safe, even when it actually isn't.
- Not knowing how to properly deal with pawn storms on the flanks.
-  Not know how to react to a minority attack with pawns.
- Not knowing how to play with / against an isolated pawn. 
- Not understanding when you make color weaknesses by pushing pawns incorrectly. 

to name a few.

With that being said, the Kmoch book Pawn Power or Soltis or Baburin's more recent books on the subject would be a good place to start.

There are a lot of interesting books and chapters on defence:

Paul Keres. 1964. "How to defend difficult positions" in Paul Keres and Alexander Kotov. The Art of the Middle Game.

Lev Polugaevsky and Iakov Damsky. 1988. The Art of Defence in Chess.

Ludek Pachman. 1972. Attack and Defence in Modern Chess Tactics.

Igor Belov. 1998. "Training Session: Making Difficult Choices." Mark Dvoretsky. "Virtuoso Defence." and "Errors and What Lies Behind Them." in Mark Dvoretsky and Artur Yusupov. Attack and Defence: How Creative Thought Develops in a Player.

Jonathan Tisdall. 1997.  "The Art of Playing Bad Positions." in Improve Your Chess Now.

Mihail Marin. 2003. Secrets of Chess Defence: Learn How to Defend and Counter-attack.

There is also The Art of Defence in Chess by Andrew Soltis

Another good book is Starting Out: Defensive Play by Angus Dunnington (Everyman Chess).

Any good books on the Sicilian?

If you can find a used copy somewhere Andrew Soltis's book on Chess Defense.........

http://www.amazon.com/Art-Defense-Chess-Andrew-Soltis/dp/0679141081/ref=sr_1_1?s=books&ie=UTF8&qid=1366081658&sr=1-1&keywords=andrew+soltis+chess+defence

or this one by Lev Polugayevsky:

http://www.amazon.com/Art-Defence-Chess-Iakov-Damsky/dp/1857441540

Studying either book carefully will make you a much stronger defensive player if you put in the work and time it takes to master the material.

And nobody says  the extraordinary book, perhaps the best that have been written about the defense in chess, with examples of Lasker and Petrosian games? The quality of Text, explanations and analitic work is fantastic! Read what Watson and Silmanm wrote about this book!
Colin Crouch "HOW TO DEFEND IN CHESS"

Alas ... Colin Crouch is one of the best chess writers in the world. . Some of his books are gems of chess literature!

Good Luck in finding this book! And is reading in a refreshing view of the the "Giants walls" in chess:  Emanuel , and Armenian Iron Tiger.

I, too, love Crouch's "How To Defend In Chess". Excellent book!