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.