There is a nice book about PalmOS history: David Pogue's book "Piloting Palm", you really should get a copy and find out about the history of the Palm OS platform and the PDA market.

It's very interesting. Also quite good is the talk that David gave.

It starts out with some funny tech support calls (I personally love this kind of stuff), after that the book explain good and bad user interface, highlighting problems in the Windows UI.