Here is a list, in no particular order, of books I’ve found essential (though not without thier flaws) to understanding design on both a philosophical and practical level. Some of these titles will appear in my the Book Review section.
User and Task Analysis for Interface Design
by JoAnn Hackos and Janice Redish
Creating Breakthrough Products
by Jonathan Cagan and Craig Vogel
Universal Principles of Design
by William Lidwell, Kritina Holden, and Jill Butler
Desinging Visual Interfaces
by Kevin Mullet and Darrell Sano
About Face 2.0
by Alan Cooper and Robert Reimann
Making Use
by John Carroll
Crossing the Chasm
by Geoffrey Moore
The Innovator’s Dilemma
by Clayton Christensen
Contextual Design
by Hugh Beyer and Karen Holtzblatt
The Art of the Long View
by Peter Schwartz
Good to Great
by Jim Collins
The Rhetoric and the Poetics of Aristotle
by Aristotle
Media Analysis Techniques
by Arthur Asa Berger
The Mythical Man Month
by Fred Brooks
The Writer’s Journey: Mythic Structures for Writers
by Christopher Vogler