Upspin sounds interesting.
There are other interesting articles, for example
https://commandcenter.blogspot.com/2019/01/notes-from-1984-trip-to-xerox-parc.html
https://commandcenter.blogspot.com/2018/02/cerns-ipod-like-control-devices-from.html
Ironically, I found this via
https://ambrevar.xyz/links/index.html
where both Kernighan and Ritchie's book "The C programming language" and Kernighan and Pike's "The Unix programming environment" are classified as "Unix books you’d rather not read".