One genre of popular fiction...
One genre of popular fiction is the mystery story, sometimes known as the "Who Dunnit?" The Apostle Paul is preoccupied, too, with the issue of "mystery" in this passage. There is the mystery made known to him in revelation, "the mystery of Christ," and "the plan of the mystery hidden for ages." But Paul is not concerned with the idea of mystery in terms of solving a crime and capturing the culprit.
Instead, he discusses the hiddenness of God's extraordinary love as it becomes revealed in all the common human ways of listening, seeing, and speaking.