Meet Amy (14 - the bookworm) and Dan (11- the pranker/computer-savvy kid) Cahill, two orphans living in Boston, MA with their terrible great Aunt Beatrice. The only thing they really enjoy is their visits every-other weekend to see their grandmother, Grace. But even seeing her is about to be taken away from them - Grace is an elderly woman, and her life is coming to a close. At Grace's funeral, Dan and Amy are brought into a room of Grace's mansion with many other of their relatives. Here, they find a video message from Grace, at first just stating general knowledge about their family: that it consists of 4 branches - Thomas, Janus, Lucian and Ekaterina (Ekat for short), and that each branch is pretty much rivals. What they don't know is they didn't just disagree on trivial family disputes, but individuals from each branch have been competing for the ultimate prize - virtually unstoppable power in a currently unknown form. But it's not out in the open: Generations of Cahills have been hiding it, by burying clues all over the world. The competition is vicious, and its life or death. They are all offered a choice: 1 million dollars each... or the first clue. They figured that if they chose the money, Beatrice would find a way to take it from them, and they would go back to their normal lives. So they decide to dive head-first into the clue hunt. With Beatrice furious and unwilling to help, they can't travel the world without a guardian. They decide to turn to their former au pair (the only one they actually liked), Nellie Gomez. Together, the team is the underdog, but the others soon find out they can't afford to ignore them.
The authors do a great job of intertwining world history with Cahill family history. It really sparked my interest in some of the countries they visited - you might even learn a thing or two :).
A cool thing about this series is you solve the puzzles along with the characters: not only in the story, but in the physical book itself! There's clues in the cover and pages that can help you unfold what will happen later in the book. It actually really exhilarating :). They are a bit short compared to the books I normally read, but the multitude of them makes up for it.
These are really thrilling, and keep you on the edge of your seat. I really recommend these if you like solving puzzles or mysteries, and travel as well :)