From an advance review copy for which I thank the publisher.
This was read decently enough by Laci Morgan, but that couldn't help a story which dragged and which felt all over the place to me. Nor could it help one of the characters, who I found obnoxious. Obviously this story isn't written for me, since I'm far from a middle-grader, but I've listened to and read many such stories before, and enjoyed a lot of them, so it wasn't the age range; it was the story itself.
Let me put in a minor qualification in here. This was an audiobook, and I listen to my audiobooks while out in the car commuting and doing other stuff. A book which deals in alphabetic cyphers and math problems really doesn't lend itself to that sort of listening, because you cannot see the printed word and study it, so the advisability of having this as an audiobook in the first place became questionable to me once I'd listened to a significant portion of it.
The story is of three youngsters, "math whiz" Charlie, his sister Anna, and another girl who they meet, named Emily. All three are with their families, spending time at an old house which has been turned into a hotel. I do believe it was explained how they came to be there, but I either missed the details or I've forgotten it, so I can't tell you. It's not really important.
In the course of their exploring the place, all three find clues to a mystery, but by the time I quit the story, they had solved nothing despite getting into everything, and the story really was dragging for me by then. The description indicates that they work together, and I'm sure they do, but the fact that by almost two-thirds the way through, they were barely on speaking terms was a problem and evinced very little in the way of cooperation or faith in them as a team.
On top of that one of them finds some old letters which were read out in full in the story and were tedious to listen to. They felt like a ball and chain on the story. Maybe they were supposed to be clues, but they sounded more clueless to me. Consequently, around sixty percent in, I decided I'd had enough of this and DNF'd it without any regrets. Younger readers might have more patience with it than I, but I wouldn't bet on that.
I was put off the story quite early by Anna, who was frankly a nightmare. She had no boundaries, no sense of personal space or privacy, and was an unrepentant pain-in-the-ass troublemaker of a child who would wander around routinely into places she didn't belong - and knew she wasn't supposed to be there - yet she never felt bad about it or had any problem with being a busy-body, an unregenerate rule breaker, and a meddling little demon. I disliked her pretty much from the start.
How you can pretend there's an explorer's "code" and then feature a hobgoblin like Anna was the only real mystery here for me. Charlie and Emily, by contrast were such bland characters that they never really registered with me as anyone to pay that much attention to. Emily was mildly obnoxious, but was a milksop compared with Anna. Charlie was a one-note character as were most of the people in this story for that matter. Charlie was bland to the point of fading into the woodwork he studied so intently.
So, overall, not a good experience, and I certainly cannot commend this as a worthy read.