Like all of Traci Hunter Abramson’s books, I read this series out of order. I started with “Royal Heir” (book 4), then read books 1, 2, then 3.

“Royal Target” (book 1) is set in a make-believe fairy-tale-ish country somewhere between Italy and France. CIA agent Janessa Rogers is asked to be Prince Garrett’s personal guard, but to protect her cover, she pretends to be his fiance (no way that can go wrong). 😛 As with almost all of Abramson’s books, I skipped the scenes from the villain’s perspectives because I hate dramatic irony. Seriously, don’t spoil the book within the book.
“Royal Secrets” is a stand-alone sequel. It’s about two different people (Prince Garrett’s older brother and Janessa’s fellow CIA friend), but I can’t imagine enjoying it as well without previously reading the first book, since about 50% of the plot deals with continued problems from the first book.
“Royal Brides,” (book 3) is a little more stand-alone. Sure, it deals with the weddings of both couples of books 1&2, but it focuses on Janessa’s brother, who–guess what–is also CIA (and Janessa doesn’t even know it), and the daughter of two servants at the chateau summer home. Though the servants are fairly prominent sub-characters, the daughter was mentioned once in the previous two books and allows this book to stand more solidly on its own.

“Royal Heir” (book 4) is about Levi. A fellow CIA agent working as the head of security at the chateau (where Janessa and Garrett live). He’s basically asked to take a princess into Witness Protection and pretend she’s his girlfriend (again, no way that can go wrong). 😛 From someone who hadn’t read any of the other books in the series, I still enjoyed it. There were references to events and relationships that happened in the previous books, but they were explained enough that I didn’t feel confused at all (just interested to read the other books too).
PS. I hope there’s a book 5 about bomb-sweeping Alan with his dog, Max.