!!!!Help using only the plot of a thriller book!!!!

[Lowri]

Can anybody remember the author or title of a book with a plot consisting of the following :

Female and Male character. Female has a Son. She has a tragic past, something to do with a fire years ago. Towards the end she dies in a fire but is reincarnated as the male character. He then becomes her in body. The Son is very suspicious as now his " mum" is acting differently. The " mum" then plans of getting rid of the Son and it ends ! Its such a shocker at the end. One of the best twists Ive ever read. Help me to locate this book please! It was probably realeased between 2014-2016. 

Thank you.