Spare Room by Dreda Say Mitchell

Lisa can't believe her luck when she finds a beautiful room to rent in a large house.

The live-in owners are a kind and welcoming couple. Everything is fine until she finds a suicide note hidden in her room. But when the couple insist this man didn't exist and that Lisa is their first tenant, Lisa begins to doubt herself.

Compelled to uncover the secrets of the man who lived in the room before her, Lisa is alarmed when increasingly disturbing incidents start to happen. Someone doesn't want Lisa to find out the truth.

As the four walls of this house and its secrets begin to close in on Lisa, she descends into a hellish hall of mirrors where she's not sure what's real and what's not as she claws her way towards the truth . . .

This room has already claimed one victim? Is it about to take another?