Cahills vs. Vespers Series (1-3)

Title(s): The Medusa Plot, A King's Ransom, The Dead of Night
Author: Gordan Korman, Jude Watson, Peter Lerangis

What is the series about?
The series is about the Cahills and Vespers fighting. The Vespers are capturing  the Cahills and threatening to kill them. Dan and Amy Cahill have to keep their family alive by doing what the Vespers tell them. They won't kill them if Dan and Amy Cahill do what they say.  They have had to steal things from museums, and they are always under a strict time limit of 4 days.
 
How is it similar to the 39 Clues series?
It's similar because there are some of the same characters, like Dan and Amy Cahill. Some other chracters come back, too, like Nellie (the Au Pair), Fiske (their uncle), Uncle Alistair Oh (another uncle), and Hamilton, Ian, Natalie, and Jonah. Also some of the places are the same, like Paris. They are always having to hunt for things all over the world.

How is it different than the 39 Clues series?
The difference is that there weren't any Vespers in the 39 clues series. The Cahills are all united and working together in this series of books, working against the Vespers. There are some new characters, also. Dan and Amy work with Sinead (who is like a sister to Amy), Jake and Atticus (they are brothers who decide to help Amy and Dan), and all of the Vespers (they are numbered, as in Vesper 1 through Vesper 6).

Which of these was your favorite book? Why?
The Dead of Night was my favorite book because of the traveling in the story. They traveled to Turkey, while Hamilton, Jonah and the messenger went to Pompeii. They were in search of an Astrolabe. I also liked the mystery in the series.  One twist was that Ian went to visit his mother in New York, and no one knows why. She ended the 39 Clues series as a villain and murderer. She even shot her own daughter.