Diplomatic Immunity is a callback to the earlier Miles stories, with a relatively simple espionage-intrigue related plot, and madcap heroics to save the day.

Imperial Auditor Vorkosigan's honeymoon is interrupted with an urgent message to go to Quaddie space and sort out a problem between a Barrayaran trade fleet and the Quaddie authorities. The Quaddies, genetically engineering humans designed for zero-G with four arms, didn't do a solid job investigating the disappearance of a Barrayaran officer, and shoreleaves problems nearly escalated to a shooting war. Miles cuts right to the center of the problem, and slight spoilers: there are Cetagandan black ops involved with an arsenal of horrific bioweapons. Only fast thinking and suicidal heroics can save the day.

This is a pretty average Vorkosigan novel. I can sort of feel that Bujold has said most of what she wants to say about these people.
But average Vorkosigan Saga is still a cut above most books.