The seventh book in the Mercy for Hire series, set in the Black Ocean Universe, does a bit of genre bending, as it switches from a straight up space opera to a who-done-it mystery. In the season (ok, book series don't really have seasons, but Morin tends to write in 4 book collections, and with his cinematic style it often feels like a season of good tv) where the overall story arc is Esper and her band of mercenaries (wait, aren't mercenaries supposed to, you know, get paid?) are after the Cult of Ra, it is a nice change of pace from the smash and grab fighting of the past two books.
The mystery starts early, and escalates on the cruise ship as Esper finds the informant she was supposed to meet dead. An interesting twist is this future cruise ship is actually a submarine - with the underwater theme a nice twist on the black ocean.
In an homage to Agatha Christie (both Ten Little Indians and Murder on the Orient Express) Esper must find the killer that is trapped with them as the body count starts to grow. A few plot twists and some nice character development (it is hard NOT to take some time to relax when you are on a luxury cruise ship after all) we find that no one is who they say they are, and the secrets unveiled leave us wondering just who is the killer, while the clock is ticking.
Kubu, Wesley Wesley and Tiffany also have a chance at some rest and relaxation before the proverbial excrement impacts the rotational cooling device and they must come to the rescue of their friend after the ship goes down on the way back to port.
A fun diversion, much like when you favorite tv show takes an episode to do something fun and different (and unfortunately as cinematic as the books are, you just can't really pull off a musical in print no matter how hard you try).
The one drawback is where the captain of the ship, on seeing the murder, decides to turn the ship around (which makes sense) and lock the crew away from the passengers completely. While this isolates the hero, villain and victims to add some tension, the idea of the authority in this situation (and ultimately, a captain is responsible for everything that happens on his ship (I know, it could be her ship, but this time the character IS a male)) basically removing himself from the situation completely just didn't fit. A better way might have been to move the ship troubles forward in the book and have THAT be what separates the crew from the passengers instead of the "Oh there is a murderer here so I'm going to lock you all here with the killer. Have fun!"
Forgiving that minor flaw, this is a fun middle interlude to the larger story, and left me wanting to see/read the next installment.
Because it is all fun and games . . .