Simpson describes their connection as "intense."
"Again and again, he told me he was obsessed with me, sexually and emotionally," Simpson writes in her memoir, according to People.
Although Mayer was obviously batting above his average in the looks department, Simpson admitted she felt insecure about not being "smart enough" for him. She says this anxiety triggered an unhealthy relationship with alcohol.
"I constantly worried that I wasn't smart enough for him," Simpson writes. "He was so clever and treated conversation like a friendly competition that he had to win."
"My anxiety would spike and I would pour another drink," she shares. "It was the start of me relying on alcohol to mask my nerves."
Simpson has also spoken about Mayer's infamous Playboy quotes in which he likened her to "sexual napalm."
"Yeah, that girl is like crack cocaine to me. Sexually it was crazy," Mayer said in the 2010 interview. "That's all I'll say. It was like napalm, sexual napalm."
She says the "shocking" comments broke her trust.
"He thought that was what I wanted to be called. I was floored and embarrassed that my grandmother was actually gonna read that. He was the most loyal person on the planet and when I read that he wasn’t, that was it for me,” she says. “I erased his number. He made it easy for me to walk away.”