Keep It Simple, Make It Valuable, Build It Piece by Pieceby Ron Jeffries
I recently finished this book and it has become one of my favorite technical books.
If you already feel comfortable developing software in iterations and with high quality, this book might not change radically your way of think, but sure that it can clarify many things and allows you to understand the forces and principles behind software development.
If you still feel lost in this profession, I think that this book can help you to take a giant leap forward in your career.
Even the subtitle is pure wisdom “Keep It Simple, Make It Valuable, Build It Piece by Piece”
A must for any software developer.