Yeah, just finished that one (Dream Machine) myself, excellent book. The other main one I know of is Dealers of Lightning, which centres on PARC specifically. Also quite a good book.

Another is Fumbling the Future, which discuss the apparent failure of Xerox to capitalise on their computing research (as you'll know from having read the Dream Machine, the reality is a bit more nuanced than that). Haven't read this one myself, not sure how good it is, seems well-received though.

Finally, Alan Kay is quite active on Quora these days, and often talks about PARC-related material: https://www.quora.com/profile/Alan-Kay-11 (At some point I recall him mentioning the Dream Machine being one of the best accounts of PARC's history, btw.)