Is Without A Voice a thriller?

I talked to one of my readers the other day and she said that she found Without A Voice frightening.

I can't get my head around it. It's alternately described by other readers as suspense or a thriller, but even that I can't quite figure out.  Thriller? When I think of thrillers I think of chainsaw murderers. I don't like thrillers. I don't like blood and guts and extreme violence, so I don't write it.

The book is tense, yes. It faces topics of domestic abuse, stalking, etc, but there are only two violent scenes and even those are what I would consider extremely mild. I cataloged it as suspense for a reason.

I think my idea of "thriller" must be seriously out of whack.

What do you think?  Is Without A Voice a thriller? Did you find it frightening?