Not a horror fan at all but really enjoy atmospheric books like ...
Rebecca by Daphne du Maurier
The Greatcoat by Helen Dunmore
Mr Pip by Lloyd Jones
A Monster Calls by Patrick Ness
Mr Chartwell by Rebecca Hunt and all Neil Gaiman's books.
The most macabre and disturbing book I've read is William Golding's Lord of the Flies. I hated it.