I'd give this one a 2.5 if the mysteries weren't quite so simple. Especially the ones starring Dr. Quicksolve's son, Junior, seem to be incredibly easy while others are things mostly only adults would know, like someone lying about a clutch. There doesn't seem to be a clear age group for this one, but the answers are still pretty obvious if you're trying at all.
I don't think I'd recommend this one to a friend, but hey, it was good for a thirty minute read. The cheesy names continue in this one as they did the others.