The only thing you should keep an eye on is probably the license? But I’m not the right person to discuss about licensing :/
It is normal practice to keep the same copyright notice and add your name to it, e.g for this project I forked in 2021: https://code.alienscience.org/alienscience/dnsclientx/src/branch/master/LICENSE
I enjoyed reading the Phoenix Project and learnt a lot from it. It is a classic for very good reasons.
There was another follow up book -- The DevOps Handbook that went into more detail about solutions to the problems raised in the Phoenix Project. I got a lot from the DevOps handbook but I found it quite a heavy read.
Years later I found a smaller, but super practical book, that covered much of the same subject matter -- Operations Anti-Patterns, Dev Ops Solutions. I recommend this Manning book after the Phoenix Project.
But then I haven't read the Unicorn Project yet, so that is a book for the list.