A few things that changed how I think:

• The Design of Everyday Things and Don't Make Me Think taught me that if someone can't figure out how to use something, it's not their fault. That applies to products, processes, and conversations.
• Design as Art showed me that function and beauty aren't opposites. The best solutions are often the simplest ones.
• Influence made me understand how people actually make decisions, which turned out to be useful for marketing, sales, and just about everything else.
• Man's Search for Meaning helped me get through some hard years. Suffering is inevitable. Being consumed by it is optional.
• Flowers for Algernon broke my heart and made me think differently about intelligence, kindness, and what we owe each other.