What's your most influential programming book in your professional career

I have this Design Pattern book that I find myself going back to over and over again. It is very nicely written. It is:

Head First Design Patterns

What is your most influential book in your programming career?

Hans Overkamp, Mar 14, 2011

Reply 1

Code Complete by Steve McConnell

Gerard del rosario, Mar 17, 2011

Reply 2

Patterns of Enterprise Application Architecture by Martin Fowler

Rajesh Pillai, Mar 15, 2011

Reply 3

For me it was

Clean Code: A Handbook of Agile Software Craftsmanship

Robert Varga, Mar 15, 2011

Reply 4

I do a lot of data modeling and try to adhere to common data model patterns.
So this would be my most important book:

Data Model Patterns, Conventions of Thought

Sean Healy, Mar 14, 2011