An excellent mystery, with no out of left field twists (all these made sense after being introduced) and no big plot holes. I thought it all followed one main character at first, but it made much more sense when I realized there were two different viewpoints. They are not technically separated - it just says "before" a few times.
Another thing that threw me off was the fact that we didn't learn the main character's name until page 227.
But overall, interesting idea, good execution, written well.