I'm geeking out, and I love reading about the development, design decisions and choices in OS development, particularly retro ones (Windows 9x and prior, the Mac OS, etc) The shortfalls, the evolution of the GUI.. a lot. I found some stuff on an early build of the Win95 taskbar, that was interesting..
Quick couple of examples.
And theres a website somewhere with tales of the Mac creation etc.
Any suggestions for good reads?