noun
Refers to a work (book, film, etc.) in the ghost/horror genre. The もの suffix marks it as a genre piece.
夏になると怪談ものが読みたくなる。
When summer comes, I feel like reading ghost stories.
この映画は典型的な怪談
This movie is a typical horror story.
怪談 is a ghost story itself; 怪談もの refers to a work belonging to that genre.
Compound of 怪談 (ghost story) and もの (thing, genre piece).