Erlang and OTP in Action
https://www.manning.com/books/erlang-and-otp-in-action
You build an application with increasing complexity. There are some other applications that are built along the way to demonstrate some ideas in a smaller scope, but the overall structure of the book is designed around making one application better as you learn more about OTP.
You can attack an idea without attacking a person. As long as people realize they are distinct from the code they write, you can be direct and brutal about code, without devolving into ad hominem. The problem is fostering a culture where people don't feel as if they are socially defined solely by the code they write.