Natalie Babbitt, The Search for Delicious. When I got older I could identify the emotion this book brought over me as nympholepsy, an affliction I have yet to recover from. It's about magic, and nature, and how we abandon them.
William Faulkner, The Reivers. My favorite novel. Unflinching sacrifice of our innocence.
Homer, The Iliad. Is this cheating? I don't care. Rage is our first word. I will say that jack's senior essay helped me understand it quite a bit more deeply than I could have on my own.
Do you then show me your improvement in these things? If I were talking to an athlete, I should say, "Show me your shoulders"; and then he might say, "Here are my halteres." You and your halteres look to that. I should reply, "I wish to see the effect of the halteres." So, when you say: "Take the treatise on the active powers, and see how I have studied it." I reply, "Slave, I am not inquiring about this, but how you exercise pursuit and avoidance, desire and aversion, how your design and purpose and prepare yourself, whether conformably to nature or not. If conformably, give me evidence of it, and I will say that you are making progress: but if not conformably, be gone, and not only expound your books, but write such books yourself; and what will you gain by it?Sheri S. Tepper, Beauty. Hard for me to go back to this one, but I read it perhaps twenty times when I was fifteen. I'll still read anything she wants to write.
G. K. Chesterton, The Man Who Was Thursday. In which we learn that the world is mad, but we still have our duty.
Luo Guanzhong, Romance of the Three Kingdoms. I use this book constantly to help me understand and deal with practical life. This is probably unhealthy.
Diane Duane, So You Want to be a Wizard. "I am on errantry, and I greet you."
C. S. Lewis' Narnia series. I'm not sure the effect on me was a beneficial one; I seem to have spent a great deal of my life assuming that at some point I would find a way into another world, and so didn't need to do my Social Studies homework.
Lloyd Alexander's Chronicles of Prydain. A good part of these books is about the joy of useful work, and also there is Princess Eilonwy.
Notably absent: overt religion, much philosophy (the Discourses scarcely count), any sci-fi, medieval works, or Xenophon. Hmm.