I'm really liking the light-heartedness; there's a sort of humor here I've not seen in a Christie book as yet.

Yes, the tongue in cheek tone really stands out, doesn't it? It reads a bit like a more mature version of "The Secret Adversary", except that Christie doesn't merely seem to be poking fun at her characters but at herself and the spy novel / evil world-domination conspiracy genre itself, too. I hope she stays that course ...

I'm really interested to see what happens with Victoria! Christie really seems to be having fun with that character.