For some reason I've gotten into reading children's books. Maybe only a nostalgia for lost youth or something, but I have found some very enjoyable entertainment in some of those I've read recently that were not available when I was a kid myself. The Magic Tree House series is just such.
I picked up Haunted Castle on Hallow's Eve as my introduction to Miss Osborne's work and was thoroughly delighted with it. Simple and direct, it is instructive without being pedantic, and introduces new words in contexts where their meanings are apparent-or explains them when they aren't. The story hangs together well, introducing the protagonists and some of their past exploits sufficiently to engage the reader no matter where in the series one starts.
I think that some of the better children's stories are written to capture the attention of adults as well. If an adult can read them, or reread them as an adult, and not lose interest in the narrative, the book is a good one. Children have as complex a gift for understanding plot and theme as adults do. I think years of television have made them better at it than they were when I was a kid. It's not the structure or complexity of the tale that loses them so much as the reading vocabulary. Language and relationships are probably "hotwired" into humans. The written word is something else again! The Haunted Castle on Hallow's Eve was interesting enough to keep the reader involved with the story and working through the new vocabulary.
One of the most significant things about the author's work is her background in history, literature, and culture. As she explains in the final pages of the book, she put her tale together from many sources, including English history, Welsh and Irish poetry and Celtic mythology and folk beliefs. In looking over the titles of her other stories, I see that she and her husband have been able to weave into their children's adventure stories information about historical topics of a wide variety making learning something fun to do. I say hooray for the Osbornes. I expect to read some of their other books and share them with others.