I could have easily picked any of the Harry Potter books, but I've re-read A LOT of books. Rose Madder was the first that crossed my mind.
It is, in my opinion, one of King's underrated novels.
The first time I read it I was 16, and just out of an abusive relationship. So given that this book is about a woman's exodus from an abusive realtionship, it's later about her revenge. Quite a powerful, yet triggering read for me.
This was also my first King novel.