Best defense books?

I'm thinking of Starting Out: Defensive Play, How to Defend in Chess by Crouch (mostly for the heavily annotated Lasker and Petrosian game collection so it's better than a strictly defensive book), and Practical Chess Defence by Jacob Aagard. 

Starting Out: Defensive Play is an obvious starting point given the book's name implies basic material, while the next two are for refining the skill.  Can't refine what you don't have, right?  So We need a first book on the subject. 

Aagard's book is said to be very hard, and I'm familiar with his material so I should be ready for it after finishing the first two.

What seperates modern play from romantic play is refined defnsive technique.  My goal isn't to be Petrosian or an inferior version of him but just want to defend at expert level someday.  Currently, I'm like a shark: gradually improve my position, swim forward but if I smell blood will relentlessly follow it (such as playing an unstoppable minority attack if black can't defend against it, usually if he doesn't know how to play Carlsbad structures)... but if I can't go forward I'm essentially dead =( 

There are three books worth getting on Defense if your going to seriously study and tackle the subject...........

1) The Art of Defense in Chess by Andrew Soltis

2) The Art of Defense in Chess by Lyev Polugayevsky

3) Secrets of Chess Defense by Mihail Marin

Aquiring skill and experience takes time and alot of hard work don't expect instant results no matter who's book you buy.

The book you should read now and re-read twice or more is Nimzowitch My System. 

My System is great, but it's too general and I'm working on defense next month not planning.  Planning is one of the three basic components of chess (the others being positional assessment, which one should revolve a plan around and analysis, which is visualizing many moves ahead to see which move maintains the advantage or leads to equality depending on the current position).

One can never read My System or Think Like a Grandmaster enough =)

Yeah I know about the three weeks to automate a skill, which is why I'm doing a book per month.  I'm currently on Dvoretsky's Endgame Manual and some of those problems are tough!  I only got a couple completely right so far (i.e., my primary variation was the one given in the solution.  Other times I'd be somewhat right but not calculate as deep as the solution went, and of course others I didn't get right at all)