Looking for a thriller about a true crime author in a haunted house

Ok so basically, there’s this cult leader/serial killer who refuses to speak to anyone about what he did, but he sends this washed true crime author a letter saying if you live in my house I’ll tell you everything. The author takes him up on this offer and it ends up being haunted with his victims. He also has a daughter who’s emo and angsty. PLEASE PLEASE PLEASE help me find this it was SUCH a good book