In "The Last Book in the Universe" by Rodman Philbrick, the protagonist emphasizes the value of memories over material possessions. The quote "The only real treasure is in your head" reflects the idea that personal experiences and knowledge are far more valuable than physical wealth. Unlike diamonds, memories cannot be taken away, providing a sense of security and worth that is intrinsic to one’s identity.

This perspective highlights the significance of one's internal world, suggesting that true richness comes from the thoughts, feelings, and experiences we accumulate throughout our lives. It encourages readers to cherish their memories, as they form the essence of who they are and can bring comfort and joy, regardless of external circumstances.