This first impression jumps straight into the action, and surrounds you with an alternate London. It doesn't, however, fully explain what is going on...I guess we'll learn with Fern; although the reader was present at her mother's death, so we have a bit more insight than Fern. There is something familiar about the story and concept of parallel worlds - it feels a bit The Secret Runners of New York-ish, I enjoyed that so I'd give this one a read too. Not too sure whether I like the cover or not.