Mind the Gap is an engrossing book that never quite goes far enough into the fantasy world for my tastes; it merely dances on the edge between fantasy and the real world, keeping more toward the reality side. When Jazz first retreats into the abadoned parts of London's subway system, I expect and hope she's going to hook up with something horrific, or wondrous. But instead she just falls in with a modern-day Fagan and his band of child thieves living in an old bomb shelter, and becomes a female Oliver Twist. She does have a few ghostly encounters underground, but nothing ever really comes of them, until the very end, at least. There are a lot of eldritch sparks flying throughout the book, but they never really catch fire. Jazz is merely an observer of the ghostly, until the end of the book. "Oh, look, ghosts."
It's a fairly pedestrian brush against a fantastical and hidden world that never quite materializes. The things you sense lurking in the shadows never reach out and grab the characters; the things that go bump in the night bump almost too softly to be heard. The authors tease us with abandoned, bricked up tunnels and doorways that hint at secrets beyond, but they never actually tear the bricks away and take us into those tunnels or through the doorways to reveal the secrets. I want to explore these hidden, forgotten places that the authors hint at, but instead they keep taking us back topside to the real London, dragging us along on the main character's adventures in cat burglary, and her involvement with a master cat burglar who turns out to be something more.
The authors do an excellent job of creating numerous moments of supernatural tension. But the tension is never really unleashed in a startling burst; it just sort of fizzles away. But it's a well-told story, extremely well-written, with a lot of tense moments. It hooks you at the very beginning and keeps you hooked, taking you on a fast-paced, entertaining literary journey that reaches a frenzied, satisfying ending. It does its job well enough, so I can't complain if the journey doesn't take me exactly where I want it to.