I vaguely recall reading Soul of a New Machine years ago, but I don't recall there being a lot of SWE lessons in it. Maybe it was because I read it so long ago. Mind sharing a few things you got from this book?

It's been a long time since I read it as well and I knew the hardware/microcode people in the book better than the OS folks--and I think the book probably focused on them more. Maybe it's not really SWE lessons per se as so much as just a really good account of a computer systems project. (I worked at Data General for many years though I joined a few years after the events of the book.)

Showstopper (about the development of Windows NT) is more focused on software obviously.

The greatest lesson I took from the book was "no mode switch".

This is an excellent principle for software development as well IMO.