Books on Operating Systems History?

An introspective member of Clan Anonymous Coward asks: "Having moved to Linux only recently from Microsoft I have become interested in the history of computer systems and how they evolved. Does anyone know of a really geat book that would go through this history, ideally centred around Unix (and all of its variants) but including other systems like IBM, Next, Apple, Microsoft, Sun and everyone else in a way that would show how we got to where we are today? Webpages would be nice suggestions, too, but it's really a good read I'm after."