The Timeless Way of Building by Christopher Alexander.
It really made me reconsider the process and ultimate goals of building systems beyond housing, and how to make pattern languages for any system I build, especially software systems.
I studied urban planning in grad school, but didn't discover Alexander until I learned that my favorite band Phish had modeled their work on a Pattern Language.
It really made me reconsider the process and ultimate goals of building systems beyond housing, and how to make pattern languages for any system I build, especially software systems.