Jules Jones

I think it will work as a standalone (Charlie's done a good job of incluing new readers), but the nature of it means that it gives you some spoilers for the first book, and you'll need to pay a bit more attention to the stuff giving you the universe background info. So if you can easily get hold of The Atrocity Archives, I'd recommend backing out and starting at the beginning. Otherwise, keep going, and read TAA later.