I'm amazed this was made in Game Maker! Unfortunately, I get sick from playing first person games, so I had to stop playing, but it was pretty interesting for the length of time I managed to play.
I like how you could speed up the text. Nice polish. :)
To be honest, I never played a mystery game in my life, so I can't really say how good it is with respect to the genre. What I can say is that your menuing system is awesome. :)