Sometimes, taste can be predictable. The pantheon for teenagers trying to flex their reading habits typically includes The Great Gatsby, Catcher in The Rye, or 1984. But even before becoming a CEO who tries to position himself apart from other CEOs, Elon Musk was trying to break from the mold, shirking the usual classics in favor of famous sci-fi lit. It differentiated him from his peers, but was nonetheless a predictable move for the man behind SpaceX and OpenAI.

Musk found that sci-fi addressed a curiosity brewing during his teen years in a way that religion and science alone couldn’t. Neither gave satisfactory answers to his questions about where the universe came from and why it exists, Walter Isaacson wrote in his new biography of the CEO, titled Elon Musk.

“When he reached his teens, it began to gnaw at him that something was missing,” Isaacson wrote. That feeling led to an “adolescent existential crisis” that Musk tried to solve with books.

“I began trying to figure out what the meaning of life and the universe was,” Musk said. “And I got real depressed about it, like maybe life may have no meaning.” He turned to existential philosophers like Nietzsche, but they left him feeling more adrift (he doesn’t recommend this as teenage reading material). He found solace in the supernatural world instead.

Three authors and books, Isaacson wrote, guided Musk through this phase and to the other side of trying to colonize Mars and bringing robots to life in a way that benefits, rather than harms, humanity.

The Moon Is a Harsh Mistress by Robert Heinlein

A favorite of Musk’s, this novel takes place on a lunar penal colony ruled by a supercomputer called Mike. The AI surpasses its robot state “with self-awareness and a sense of humor,” Isaacson writes, which leads to its self-sacrifice during a rebellion.

“The book explores an issue that would become central to Musk’s life: Will artificial intelligence develop in ways that benefit and protect humanity, or will machines develop intentions of their own and become a threat to humans,” Isaacson explains.

Musk would soon grapple with this question when he helped found OpenAI in 2015 alongside Sam Altman. He has often spoken about the dangers of AI, arguing that AI systems need safeguards to prevent them from replacing humans (a topic that he often debated with Google cofounder Larry Page, which eventually led to their falling-out). Musk’s take on AI safety formed the foundation of OpenAI’s goals “to advance digital intelligence in the way that is most likely to benefit humanity as a whole,” per a statement from the company’s website.

Isaac Asimov’s Robot series

Musk found more future AI bait in Isaac Asimov’s series of 37 short stories and six novels centered around, you guessed it, robots. The work grappled with the same topic of AI ethics that Heinlein’s work did. “The tales formulate laws of robotics that are designed to make sure robots do not get out of control,” Isaacson wrote.

To get real dorky with it, one book names one of these rules the Zeroth Law, entailing that “a robot may not harm humanity, or, through inaction, allow humanity to come to harm.” The books had a long-lasting impact; as Isaacson points out, Musk tweeted decades later that “Foundation Series & Zeroth Law are fundamental to the creation of SpaceX.”

This was yet another influence in Musk’s quest with Altman to found OpenAI in a way that benefited humanity. The issue of “AI alignment” aimed to align AGI (artificial general intelligence) with human values and intent—much like how Asimov’s rules in his novels were meant to hinder robots from taking over.

The Hitchhiker’s Guide to the Galaxy by Douglas Adams

Hailing this classic as the novel that most influenced Musk’s “wonder years,” Isaacson wrote that it “helped shape Musk’s philosophy and added a dollop of droll humor to his serious mien.” Rather than making thinly-veiled jokes as Musk tends to do, Adams had more of an ironic take that Musk said helped dig him out of a depressive state.

The story is also centered around understanding the meaning of life. In it, citizens give a supercomputer the task of answering what the universe’s purpose is, which answers with “42” 7 million years later. “The problem, to be quite honest with you, is that you’ve never actually known what the question is,” the computer told the shocked crowd.

Seemingly, Musk brings the lessons from this galaxy—along with his later interest in video games—into every venture that he explores now. “I took from the book that we need to extend the scope of science so that we are better able to ask the questions about the answer, which is the universe,” he said, a thought he has carried with him in creating his own AI venture, xAI, after leaving OpenAI in 2018 when Altman rejected his proposal to run the company.

He said in a July Twitter Spaces Talk that xAI aims “to build a good AGI with the overarching purpose of just trying to understand the universe. The safest way to build an AI is actually to make one that is maximally curious and truth–seeking.”

AI innovations can certainly start to feel supernatural and ring eerily of any famed sci-fi story, as investors poured billions into tech advancements in the field earlier this year. Taking a page from his favored books, Musk told US senators AI was a double-edged sword last week during a summit on the topic and made a plea for regulation on deeper AI.

As one of the early inventors in the field of AI, Musk wants to avoid becoming like the sci-fi trope he once studied, an ego-based scientist who could one day lose control of his invention. Yet he’s since regretted walking away from OpenAI, calling himself “a huge idiot,” for doing so. Perhaps curling up and reading a book can salve the sting.