Ordinary Love by Marie Rutkoski

There's no such thing as an ordinary love story
 
When Emily catches sight of Gennifer Hall at a party, she is transported back to the moment they fell in love as teenagers. Their connection was electric, and they thought it was forever.
 
Twenty years late, Gen is an Olympic runner, the career she strived for, while Emily is living a picture-perfect life with her two young children and wealthy husband, Jack.
But Jack's controlling behaviour is spiralling, and Emily has lost sight of who she once was.
 
Now, despite Emily's fracturing marriage and the pressures of Gen's career, they are drawn back together by a magnetic attraction. After years of heartbreak, missed chances and misunderstandings, will they finally get a second chance at first love?