This is hilarious satire drawn from the author's personal, all-too-real experience of working with diplomats. As the jacket cover says, Retief is a James Bond among timid, ass-covering diplomats, with predictable hilarity. It's a fantastic concept.
I'm not sure what possessed the editors of this book to put the one serious Retief story first. It's an ok story, but in a completely different tone from the rest of the book, having none of the delightful satire. It also is supposed to (I think) occur a lot later in time than the rest of the stories, so its presence at the beginning is just confusing. The reason why people read Retief is the other stories.
The rest of the book consists of short stories which are composed of three parts: (1) hilarious satire where the diplomatic team proves its utter inability to negotiate its way out of a paper bag, followed by a James Bond story where Retief smoothly and debonairly accomplishes what entire government task forces could not, followed by more hilarious satire as the team of idiots attempts to claim credit for it.
I'm not as much of a fan of the middle action-adventure parts. Like a James Bond story, they have have humor and adventure, and for the most part, they are ok drama stories. Unfortunately, drama sits a bit uneasily with the silly beginnings and the endings. And in some cases, you also just cannot take the villains very seriously either, which again detracts from the drama (or the drama detracts from the satire). There is some decent SF world-building in some of them, but sometimes I thought it dragged. Mostly, I wish he had just shortened those parts, especially for the longer stories. After reading the hilarious introductions, you're not really in the mood for a grip-your-seat adventure story.
There are other Retief stories out there which are not collected in this volume, but in my opinion most of them are just not as good as the ones here (they drag even more in the action-adventure part). The editors did a good job of selecting stories.
This book used to be in the Baen free library, but they pulled it, unfortunately.