Dr. Fell and the Playground of Doom
Only Jerry, Nancy, and Gail are immune to the lure of his extravagant wonderland. And they alone notice that when the injuries begin to pile up on the jungle gym, somehow Dr. Fell is able to heal each one with miraculous speed. Now the three children must find a way to uncover the doctor’s secret power without being captivated by his trickery.
The appeal of playgrounds is very strong, especially for middle school children, who often have to spend long moments after lunch standing around on sidewalks, and who are probably routinely told that they are too old to be on playground equipment if they are brave enough to venture forth onto it. I can't think of any other novels that use this particular back drop as a story setting.
The world building is especially good in this, especially toward the end when the children are helped by someone who knew Dr. Fell years earlier and had fallen prey to to his schemes as a child. The explanations made sense, and the forces of evil encounter were deliciously scary.
I was apprehensive about the somewhat twee names in the book (Vexington Avenue, Von Burden Lane) and the repetition of certain phrases (Old Lady Witherton could not be bothered), but these would add to the read aloud qualities of the book, and show the author's background as a storyteller.
Hand this one to readers who enjoy spooky tales set in magical schools-- Loftin's Sinister Sweetness of Splendid Academy, Gilman's Tales from Lovecraft Middle School or Stewart's Mysterious Benedict Society, although the book that this most reminded me of, for reasons I can't fully explain, was Ray Bradbury's Something Wicked This Way Comes!