I recommend reading the Bhagavad Gita. There is a version of the Bhagavad Gita with commentary from Yoganada where he breaks it all down to fulfill an inquiring mind. The Upanishads appeal to me as well but more from a poetic level.
"One who is devoted to yoga attains peace by renouncing the fruits of action. But one who is not united with yoga is impeller by desires, attached to the fruits of action, and therefore, goes to bondage."
"Knowledge is better than repeated effort, and better than knowledge is meditation. From meditation follows renunciation of fruits of action, and from renunciation there arises ceaseless peace"
- Bhagavad Gita
"Whatever the content of consciousness at the time of death, that is what unites us to prana, udana, and the self, to be reborn in the plane that we have earned. Those who realize this go beyond death. Their children too follow in their footsteps. Those who percieve how prana rises, enters the body, and becomes five fold to serve the Self, they do not die; they do not die. "
"There is only one way to know the Self, and that is to realize him yourself. The ignorant think the Self can be known by the intellect, but the illumined know he is beyond the duality of the knower and the known. The Self is realized in a higher state of consciousness when you have broken through the wrong identification that you are the body, subject to birth and death. To be the Self is to go beyond death. Realize the self, the shining goal of life! If you do not, there is only darkness. See the Self in all, and go beyond death. "
- Kena Upanishad