These books are my top "theory" picks for software professionals:

1. 
   Mythical Man-Month
   by Fred Brooks
2. 
   Code Complete
   by Steve McConnell
3. 
   Pragmatic Unit Testing
   by Andrew Hunt,Dave Thomas
4. 
   Design Patterns
   by Erich Gamma
5. 
   The Pragmatic Programmer
   by Andrew Hunt,Dave Thomas
6. 
   Refactoring
   by Martin Fowler
7. 
   Agile and Iterative Development
   by Craig Larman