Elon Musk might be the internet's worst boyfriend. At least that's what it seems like in his new biography.

• Elon Musk doesn't appear to be an easy person to date, it's revealed in a new biography.
• In the book, some of Musk's former partners detailed instances where they said he was emotionally volatile.
• Musk's ex-girlfriend Grimes, the musician, said he can fly into "demon mode" at times.

What's it like to date the richest man in the world? It appears to be far from all glitz and glamour. Walter Isaacson's biography of Elon Musk paints a somewhat sobering picture.

It turns out, dating the tech mogul means spending a lot of time hanging out at Tesla and SpaceX factories, sitting in on late-night business meetings, testing out new Tesla protoypes, and discussing the dangers of artificial intelligence, according to the book.

Musk's girlfriends get a front-row seat to some of his historic decisions, but the fun sometimes appears to end there. Some of the women in Musk's past describe the relationship as emotionally volatile.

"Elon and I were used to having big arguments in public," Musk's first wife, Justine Wilson, told Isaacson. "I don't think you can be in a relationship with Elon and not argue."

Wilson told Isaacson, the book's author, that Musk sometimes resorted to calling her "an idiot" or "moron" in arguments. She said in a 2010 essay for Marie Claire that he whispered to her that he was the "alpha" in the relationship during their first dance at their wedding. Wilson and Musk were married from 2000 to 2008 and had six children together.

'That lack of empathy always gives me pause'

"He's a great man in a lot of ways, but it's that lack of empathy that always gives me pause," Wilson told Isaacson of her relationship with Musk.

And Wilson isn't the only one to point out what she perceived as a lack of empathy. Grimes, Musk's on-and-off again girlfriend, told Isaacson that there are seemingly different versions of Musk — from a "chill" one to a version that flies into what she calls "demon mode."

In the book, she described "demon mode" as a version of Musk that can be unpleasant to be around, but that "gets shit done." This Musk is likely to order up a work surge or tear into an employee, Isaacson has said.

"When we hang out, I make sure I'm with the right Elon," Grimes, who is legally named Claire Boucher, told Isaacson. "There are guys in that head who don't like me, and I don't like them."

In the past, Musk has denied allegations related to reports that he has flown into rages at work and fired staff, saying he gives "clear and frank" feedback to employees. He didn't respond to a request for comment for this story.

Meanwhile, Grimes told Isaacson that she feels the billionaire "associates love with being mean or abusive." In the book, Isaacson wrote that Musk's relationships with women "often involved an unhealthy dose of mutual meanness," detailing an incident where Musk called for Grimes to "shame him for being fat."

Musk appeared to have had a similarly tumultuous relationship with Amber Heard, who he dated briefly in 2017. In the biography, Musk called the relationship "brutal" and said the pair would sometimes fight through the night to the point that he had difficulty functioning the next day.

Still, Musk's first wife told Isaacson that Musk struggled to understand what it means to have empathy. As for her part, Grimes said she feels Musk's behavior is misunderstood because he has Asperger's syndrome, a diagnosis he first revealed during a 2021 episode of "Saturday Night Live."

In the book, the singer said she was "horrified" after Musk sent a picture of her having a C-section to her father and brothers. Grimes gave birth to their first child X Æ A-Xii Musk, referred to by his parents as "X," in May 2020.

"It was Elon's Asperger's coming out in full," Grimes told Isaacson. "He was just clueless about why I'd be upset."

Musk isn't your typical billionaire

Musk's intense work ethic also means he's not likely to take his girlfriend on a lavish vacation, subbing time overseas or on a yacht with hours spent visiting him during work sprints where he's slept in the office or sitting in on late-night meetings.

For example, Musk postponed his honeymoon with Wilson by months so that he could sort out X.com's merger with PayPal in 2000, Isaacson said. They later had to cut the honeymoon short due to turmoil at the company, according to the book.

Grimes has commented on Musk's lifestyle as well in the past. Last year, she said Musk "lives at times below the poverty line," saying it was "to the point where I was like, 'Can we not live in a very insecure $40,000 house? Where the neighbors, like, film us, and there's no security, and I'm eating peanut butter for eight days in a row?'"

For his part, Musk does not live the lavish lifestyle of the typical billionaire. Musk announced he intended to sell all of his possessions and "own no house in 2020. He sold his last house in 2021 and has said he's renting a house in Texas from SpaceX that cost $50,000.

The billionaire also appears, at times, to not value full transparency. Isaacson wrote that Musk kept his decision to father twins with Neuralink director Shivon Zilis via IVF from Grimes, who only learned about the babies after it was revealed to the public by Insider last year.

At one point, Isaacson said both Grimes and Zilis were in the same hospital — Zilis with complications from her pregnancy and Grimes visiting the surrogate who was carrying her second child with Musk. But neither women knew that the other was in the hospital or that the other was planning on having a child with Musk, according to Isaacson.

Sometimes he has a tender side

Despite some of the apparent difficulties of being in a relationship with Musk, the billionaire can be tender at times, including in his relationship with his children, it's revealed in the book. Isaacson wrote that Musk took his three-year-old son X virtually everywhere and has worked to be an active presence in the lives of his twins with Zilis.

Musk's second wife, Talulah Riley, told Isaacson that when her close friend died, he flew to England to be with her. Musk and Riley were married twice, from 2010 to 2012 and 2013 to 2016.

"We just watched stupid TV and laughed and hung out and he just made me laugh instead of cry," Riley told Isaacson of Musk's trip to visit her in 2021.

Musk and Wilson, as well as representatives for Grimes, Riley, and Heard, did not respond to a request for comment ahead of publication.