Great book I've been reading is The Mind of Madness by Richard Bentall. It talks a lot on how our current system of diagnosis is largely just built upon trends we went with back in ye olden days. Great read on how and why we diagnose the way we do and questions whether it's truly the best way to do it.
EDIT: sorry guys I got it confused with a different book! Title is Madness Explained. Has a pic of Van Gogh on the cover on Amazon.
https://www.amazon.com/Madness-Explained-Psychosis-Human-Nature/dp/0140275401