It Ends with Us - Colleen Hoover

Lily hasn't always had it easy, but that's never stopped her from working hard for the life she wants.  She's come a long way from the small town in Maine where she grew up - she graduated from college, moved to Boston, and started her own business.  So when she feels a spark with a gorgeous neurosurgeon named Ryle Kincaid, everything in Lily's life suddenly seems almost too good to be true.

Ryle is assertive, stubborn, maybe even a little arrogant.  He's also sensitive, brilliant, and has a total soft spot for Lily, but Ryle's complete aversion to relationships is disturbing.

As questions about her new relationship overwhelm her, so do thoughts of Atlas Corrigan - her first love and a link to the past she left behind.  He was her kindred spirit, her protector.  When Atlas suddenly reappears, everything Lily has built with Ryle is threatened.