Emotionally devastating.
On its own the murder mystery that the fmc, Harlow, deals with would have been a thrilling story and Belli does an amazing job delivering that. While delivering that though she also portrays the tragedy of 9/11 and how it left a lot of people with heavy trauma. She adds in the layers of how so many people may have felt after experiencing such a devastating shock and how they may have dealt with it after.
If Belli didn't experience it herself she definitely did the work to research it and properly write it.
The only reason its not a 5 star book is because of how much Harlow refused to think buuuut that should be accredited to the trauma she experienced and refused to process (so Belli did her job their I guess lol).
*Spoiler below*
The chapter of Harlow actually having been in the towers and what she experienced when everything happened was especially striking to me. The ending with Mia was a perfect addition.