Amy and Dan Cahill's quest for the 39 Clues continues into Austria, with the other five remaining teams hot on their trail. They don't know who to trust, but still have their resourceful au pair, Nellie Gomez in tow. Where the last book was based on the life and inventions of Benjamin Franklin, this one revolves around Wolfgang Amadeus Mozart and his sister Maria Anna "Nannerl" Mozart - who parallel the brother-sister relationship between Amy and Dan.
This book has more plotting and intrigue, but it is does not involve the secondary Cahill characters quite as much as the first book. Iain & Natalie Kabra, Alistair Oh, and Jonah Wizard are the only ones who make any kind of major appearance in this leg of the quest, though the Holts are featured in the beginning.
It was just as fun as The Maze of Bones, and I plan on going through the entire series because I enjoyed the first two books so much.