I picked this up because recently I unknowingly read its sequel, The Green Man. I found that book to be confusing and rather vague about the dangerous magic it was describing and I was hoping that this book would shed some light on that. Unfortunately, all reading this did was raise more questions, and introduce numerous continuity errors between the two books.
The most egregious to me, which really ruined the whole experience, although it might come off as nit-picky, was the chronological setting. The premise is that a supernatural magic show occurs in a train depot in this particular town (geographical setting also unclear, though I suspect Britain or New England) every time August 8th falls on a Saturday. This is said to have already happened in 1936 and 1964. Consulting a virtual calendar, I find this data to be accurate and determine that this book takes place in 1992, although it was written in 1987. Okay. The next time this event could happen after that is 2020. However, in the sequel, a character who is approximately 13 years old is now "an old lady" with heart problems. In 2020, she would be 41, which is stretching "old lady" to quite an extent. It's more likely that the date is another 28 years later, but there's nothing to suggest a futuristic world. In fact, there's nothing to suggest that book could even take place in 2012 (complete lack of cell phones, computers, etc. even by teenagers...) It ended up just being frustrating.
If one was able to overlook that, one would next be confronted with the dullness and confusion of this plot. Miss Potts attended the 1936 show and now she's having dreams about it. Emily Endicott gets sucked in to the investigation. Neither of them uncover anything much of interest in their search, and most of the action of the book centers on descriptions of Emily's irritating younger siblings. The clock ticks inexorably toward August 8th, and the climactic final scene, which isn't climactic at all because Emily passes out and pretty much nothing happens. Boring.

i absolutely LOVED THIS BOOK!!!