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.

Some non tech book genres to add for devs and leads I think would be about the history of the computing/IT industry, labor history in general, hacker and maker culture, writings/letters of some of the researchers and engineers like Turning, Von Neumann, Dijkstra, Knuth, etc, and some classical and neoclassical literature.

Except book #2 I fully agree, these are great books to read for someone who wants to grow their non technical skills.