The word opanishad primarily refers to a knowledge of the self, knowledge of atman or brahman. The secondary meaning of penishent is the book real meaning, the knowledge that gives you enlightenment and sets you free. In vedanta, atman and brahman are the same thing. You can get any cuto penishot book if you get on market from the venanta society,. rama christian mission publications, or chinmy mission, among others. It's available from velant the press.
Swami Sarvapriyananda teaches the Katha Upanishad, which is one of the most popular Upanishads. The scripture concerns the story of a young man who goes to the house of death to find out what happens after death. The reply describes the nature of reality and the meaning of life.