This is more of the same. It's a series of random, unconnected adventures concerning the toxic, rude, abusive Mary Poppins and her charming, thankfully resilient young charges. I kind of thought (hoped?) that this book would be comprised of, basically, Mary Poppins literally opening a door, and that would be it, but there was a little more to it than that.
This one starts with a random historical discussion on Guy Fawkes Day, leading to the return of Mary Poppins via firework in the Park. From there you read about stories involving peppermint stick horses, an undersea party honoring Mary Poppins (of course) and a celebration of the New Year with a multitude of rival fairy tale characters joining forces in The Crack between the old year and the new. This book also includes the story that was adapted to an animated short and included in a recent DVD release of Disney's Mary Poppins, "The Cat That Looked At a King." So for some reason every creature in the world adores Mary Poppins (at least in the non-human world), and I still don't really get it. The parents are more oblivious than ever, the kids are still pretty fun, but Mary Poppins is more toxic than ever. She's always looking at the children with disgust and treating them like they're absolute morons for mentioning the adventures that she led them on! The strangest part is that these adventures sometimes include the entire cast or other visitors of the park, but she still is furious and mortally offended at any implication that she would do anything reproachful. How can someone claim to be "practically perfect" when she's so horribly cross all the time? The writing is still all right, and the illustrations are still charming, but it's so hard to get on board when the main character is such an unpleasant prig. Why does she keep leaving and coming anyway. Perhaps to inflict further psychological damage to poor Jane and Michael?
I don't think the series needed to continue this long, but, well, it did. There's a little of the charming, and a lot of the maddening, but the balance is obviously off. I think Mary Poppins reaches her height of unpleasantness in this third book in the series.