The Enchanted Castle
There's nothing very surprising about the characters or plot here, but Nesbit has such a deft touch with characterization that you won't mind that. She's a little too enamored of Jerry, the eldest and leader, who's frankly a bit of a jerk. And the gender roles aren't any better than you might expect, with the girls tending toward supportive roles. But overall, the story is engaging and fun. There's a magic ring, and Nesbit ensures that everyone gets a turn with it. The children explore all the things they ought to, without any of the willful ignorance these stories sometimes rely on.
The explanation for it all, which comes clear at the end, is on the thin side, but the story is romantic enough that it's easy to let it slide. There's a romance, and everything comes out just right. Mostly, though, the charm of the story is in the viewpoint of the children and how they see the adults. Nesbit has just the right touch in making clear that she, the reader, and the children are all on the same side, and in bringing humor to the mundane situations we all face. All in all, an enjoyable story.