Before Elon Musk began launching rockets into space, digging tunnels underneath Los Angeles for high-speed trains and debating the impact of artificial intelligence, he was a book-loving teenager struggling to find a sense of purpose.
At age 14, Musk was neck-deep in a self-described "existential crisis."
Grappling with the meaning of life, the preteen read philosophy books usually reserved for college students, including titles by Arthur Schopenhauer.
Not surprisingly, the depressing essays didn't help him, the SpaceX and Tesla CEO says.
"We happened to have some books by Nietzsche and Schopenhauer in the house, which you should not read at age 14," Musk told journalist Alison van Diggelen. "It is bad; it's really negative."
He turned to science fiction instead, picking up Douglas Adams' "The Hitchhiker's Guide to the Galaxy."
The story, which follows a man lost in space, made a big impression on Musk. In fact, he almost named his first Mars-bound rocketship after one in the book, called "Heart of Gold."
Adams' intergalactic story begins when a man named Arthur Dent realizes his house and the planet he lives on are about to be destroyed. To escape, Dent hitches a ride off Earth into space, only to be tossed out, mid-trip, into the galaxy.
Adrift in space, Dent struggles to find meaning in life, an experience that resonated with Musk.
The metaphysical tale encouraged Musk to ask bigger questions about subjects that interested him, such as space, the impact one person can have, technology and the future of mankind.
"It's quite positive, I think," Musk says. "It highlighted an important point, which is that a lot of times the question is harder than the answer."
"If you can properly phrase the question, then the answer is the easy part," he says. "So, to the degree that we can better understand the universe, then we can better know what questions to ask."
The science fiction read isn't the only book to inspire Musk. A biography of Benjamin Franklin taught Musk several lessons about his career, including the importance of curiosity, and William Golding's "Lord of the Flies" encouraged Musk to work to better mankind.
