I just finished reading Stowaway by D. Ann Kelley and James G. Kelley (and I happen to know the authors). Most of it takes place in Michigan, it’s kinda part of a series but it’s by far the best one yet so I’d definitely recommend this one first. It might reveal a few details from the first few books but it’s the most polished and fast read of any of the stories. The endings still end kinda quick though.
Jill Traynor returns as the main character (after the first book they started adding “A Jill Traynor Mystery” as the subtitle. One of the new characters chooses the Edumund Fitgerald as the ship to sneak onto, I think we all know how that’s likely to end. But the whole mystery revolves around the message they managed to get off the ship that reveals where the ________ is/are located. It’s got a bit of historical fact weaved in (and they clarify the details in the afterward). If you’re from Michigan or the Great Lakes area and like mysteries it’s a must read.
