In her new memoir, Open Book, the singer and fashion designer is not holding back when it comes to the musician, who she met in 2005. The musical duo first bumped into each other at a pre-Grammys party, and according to Simpson, Mayer then began writing her notes. Following her split with husband Nick Lachey in late 2005, Simpson began to date again. That's when Mayer told the "With You" singer that he "wanted to have all of me or nothing."
"Again and again, he told me he was obsessed with me, sexually and emotionally," Simpson writes in her memoir, via People.
Though they had an intense connection, Simpson admits that she felt insecure about not being "smart enough" for Mayer.
"I constantly worried that I wasn't smart enough for him," Simpson tells readers. "He was so clever and treated conversation like a friendly competition that he had to win."