I picked up What Remains because I had a great time reading Emma in the Night, also by Wendy Walker. These two titles are very different, with a common thread of a female detective that is seeking answers. 

In What Remains, Detective Elise Sutton works on cold cases. One day she is in TJ Maxx when something terrible happens and all of her law enforcement training becomes very useful. Unfortunately, she struggles with the mental weight of that day and the man whose life she saved becomes the man who haunts her. 

This is a cat and mouse thriller, so it did have steady tension. I was engaged throughout, but I think it lacked the character relatability that I found in Emma in the Night. I think this will be great for readers who like more tension and military/police perspective as well as crime analysis.