You can't go wrong! His most important treatise - and the book I talk about more with UX people and software devs more than architects even - is A Pattern Langu

You can't go wrong! His most important treatise - and the book I talk about more with UX people and software devs more than architects even - is A Pattern Language. Basically the deal with Alexander is he was a VERY early adopter of computerization in architecture. He made some kinda... missteps? about systematization in his earliest writings. Then walked it all back / developed it with "A City is Not a Tree" talking about graphs and urban organization. His arc from there was constantly deeper into trying to make sense of how information science techniques could be applied, most notably in A Pattern Language and the case study of its application, The Oregon Project. Then, his "magnum opus" was a development on that where he tried to fill in the gaps that A Pattern Language left was A Timeless Way of Building. If you don't want to get too deep, I'd stick with A Pattern Language.