First time I have read this author. He is the son of Faye and Jonathan Kellerman. Back cover of book:

Saving lives is Jonah Stem's job-but he usually does it at the hospital, not at 3 a.m. on the dark streets of Manhattan. When he impulsively intervenes to save a beautiful woman from a man menacing her with a knife, killing the attacker in the process, he is transformed from an overworked medical student to a hero in the media spotlight. The woman, Eve Gones, is profoundly grateful, and wants to show it. Before long, they're engaged in a wildly passionate love affair. An affair that Eve doesn't want to end. Ever

I will leave the rest up to you to find out...book is now available...but listed at PBS. Will update it's release soon.