Into the Gauntlet

Into the Gauntlet - Book 10 - 39 Clues by Margaret Peterson Haddix

Wow! this series has been so great, mystery, intrigue, world travel, famous people throughout history, a quirky brother and sister team with their crazy nanny, and a twisted family tree, and a very serious prize that they are all after. Book 10 did not let me down, it reminded me of previous adventures and clues through the series as welll as plotting the route for this one.

Here's the write up:
Fourteen-year-old Amy Cahill and her younger brother, Dan, have had enough. Not only do they have to find the 39 Clues first, they're expected to reunite thier backstabbing family-the same people who killed their parents. But Amy and Dan haven't survived explosions and assassination attempts for nothing. They have a plan to finish the Clue hunt on thier own terms. Too bad there's a final- fatal secret the Madrigals haven't told them. A secret that could cost Amy and Dan - and the world - everything...

So I thought this was going to be the end of the series, but I think they have left the door open for these characters to go further - hint it has to do with the prize.