Congratulations to Katie! She guessed Challenge #2 correctly.
To refresh your memory, here's the clue for Challenge #2:
This book is not about Humpty Dumpty but the main character did have a great fall. Fortunately for him, he had a doctor instead of the King's horses and men trying to put him back together. The character knows his way around London, both the side that everybody sees and its newly constructed underbelly.
So the correct answer to this is (drum roll, please!):
Book Title: Montmorency: Thief, Liar, Gentleman
Author: Eleanor Updale
Way to go Katie!