Miguel Guitart & Korydon (The State University of New York at Buffalo, New York, USA) Smith 
Introducing Architectural Theory [PDF ebook] 
Debating a Discipline

This is the most accessible architectural theory book that exists. Korydon Smith presents each common architectural subject – such as tectonics, use, and site – as though it were a conversation across history between theorists by providing you with the original text, a reflective text, and a philosophical text. He also introduces each chapter by highlighting key ideas and asking you a set of reflective questions so that you can hone your own theory, which is essential to both your success in the studio and your adaptability in the profession. These primary source texts, which are central to your understanding of the discipline, were written by such architects as Le Corbusier, Robert Venturi, and Adrian Forty. The appendices also have guides to aid your reading comprehension; to help you write descriptively, analytically, and disputationally; and to show you citation styles and how to do library-based research. More than any other architectural theory book about the great thinkers, Introducing Architectural Theory teaches you to think as well.