The Calder Game
The Calder Game is the best book in the trilogy.
Even though I wasn't able to find out the code in the illustrations this time around by myself, I really liked it for a lot of reasons.
One reason is that the setting finally got out of Chicago and Balliett let us explore the world of Britain.
Another reason: The first two books introduced me to artists Johannes Vermeer and Frank Lloyd Wright, but Alexander Calder has got to be my favorite artist ever in a book.
I like how Calder's absence brought Petra and Tommy together as friends.
This is a good book.
Also google "Banksy"