All the great philosophers who try to explain everything dive into psychology. Nietzsche was the first modern depth psychologist. I just read a book called Nietzsche's Depth Psychology, which was excellent. The first part of Plato's Republic is all about psychology.

Hmm... If you like Sartre and Foucault then you might like Simone de Beauvoir's The Ethics of Ambiguity. She was one of Sartre's mistresses. She's a prolific writer and this book dives deep into psychology and types of people. It's existential. However, you could just as easily get Locke, Hume, Berkeley or Leibniz. Thomas Reid's Inquiry into the human mind was my favorite history of modern philosophy read. He's clear, concise and witty. I also have a book called Philosophy of Psychology by Daniel N. Robinson.