Diplomatic Immunity, by Lois McMaster Bujold

It may just be a reaction to finishing Bujold's best book in the series, A Civil Campaign, but Diplomatic Immunity just falls flat in some way. A happily-married Miles is a good thing, but he's lost some of the frenetic energy and forward momentum at all costs that made the earlier novels so fun. I suspect Bujold felt the same way after writing this one, leading to her long hiatus from Miles' milieu, which hasn't necessarily been a bad thing, she's written some awesome fantasy novels in that time.
Miles and Ekaterin are at the end of their honeymoon tour, about to become parents when their children are "hatched" out of their uterine replicators when they return to Barrayar. Miles gets a message from the Emperor, directing him to get his Auditorial presence to an out of the way space habitat where a Komarran merchant fleet, escorted by Barrayaran military ships, has run into a bit of trouble with the local authorities.
We end up with a reprising return to QuaddieSpace, from Bujold's earlier novel, Falling Free. On arriving there, Miles is surprised to find an old friend, the hermaphrodite Bel Thorne, serving as Portmaster, and an old rescuee, Nicole the quaddie (human genetically altered for free fall conditions with all four limbs being arms) dulcimer player whom Miles and Bel stole out from under Baron Ryoval in an earlier adventure on Jackson's Whole.
One of the Barrayaran security officers has disappeared under suspicious circumstances while in port, and a near riot caused when another man goes AWOL and the security squad sent to return him to the ship gets a little carried away has landed the squad in the quaddies' brig. It will take what diplomatic skills Miles possesses to get them released without costing the Empire too much, and his tenacious investigative skills to figure out the case of the missing officer. All of this turns out to be much more than he expects, but not, perhaps what we've come to expect from a Vorkosigan adventure.
It's a must read from a completeness point of view, but just not as good as most of the rest of the series.