Amazing book. Very readable. I highly recommend it. The book has a section call "War story" at the end of each chapter in which Skiena shares his real life experience of when the contents from that particular chapter came in handy for him.
Actually Linus studied the heck out of other codebases. For example, linux itself was inspired by UNIX and it is said that he studied MINIX (minified version of UNIX used for teaching) before he started developing linux.
https://www.infoq.com/
https://github.com/binhnguyennus/awesome-scalability
https://engineering.linkedin.com/distributed-systems/log-wha...
https://www.microsoft.com/en-us/research/blog/
https://research.ibm.com/publications