Books about self-reflection

Hey guys!! would greatly appreciate it if you can recommend me any self-help books about self-reflection.
I'm in my 20s and just realized that there are so many things I don't know about myself, there are also many things that I'm afraid to acknowledge about myself. That's why lately I'm trying to do many new things as possible; testing what I like and not.
Please recommend any book to this old man, any books that will help me reflect and find my happiness.