Things Not Seen is a very fast-moving, exciting novel that is a very hard book to place a genre on. For example, what would you say a book about an invisible person would be? Sci-fi? Or fantasy? I didn't know either, so I just put general. But that doesn't quite fit it either. General...sounds generic. Boring, simple, your everyday book. This is not that. This book stretches your brain's capacity to think of the most crazy things on Earth. You will find yourself thinking of theories and perhaps getting the next book in the trilogy!
Things Hoped For, Things That Are, (both by Andrew Clements in Things Trilogy)