Not OP but I really enjoyed Jung's: Memories, Dreams, and Reflections. I haven't read any of the rest of his work so I really can't say if this is the best place to start with him but being totally new to Jung, I took a lot away from this book. The book touches on many of his theories and gives you an idea of the arc of his life which is nice but also provides great insight into Jung's inner world which is what I found most fascinating about the book. I've never read anything else quite like it.

I believe the book introducing his theory of introversion/extraversion was Psychological Types based on his own clinical research. It's a theory, not a law.. :-)