I read this book on a lark, hoping to finish all I can by this child-hood favorite author. And then I was happily surprised to see some of my favorite plot elements mixed together: street thieves, London in the olden days (no specific dates given, but before industry), street magicians, real occult magic, a gypsy wagon and then a mystery tossed in for fun.
I do wish that there had been more of Kim's former life as a street thief included here, as well as more illusion magic but the rest of the book made up for the lack.
I was happy that I didn't figure out the Whodunit before the book came to the conclusion, since that always bugs me.
I loved all the comedy and humor found within the book as well. I didn't like how fast it ended, but I suppose thats your YA aspect of it.