I've read a lot of fantasy literature both as a child and as a young adult. My appreciation for the genre began when I first read J. K. Rowling's immensely popular Harry Potter books and grew as I explored the works of E. Nesbit, Edward Eager, Diana Wynne Jones, Patricia C. Wrede, Caroline Stevermer, and Robin McKinley. Fantasy stories, even more so than regular books, offer an escape from the humdrum reality of the real world, which I think explains their widespread appeal. Reading fantasy allows us to believe for a brief time that magic is real, and that absolutely anything is possible.
One of the most unique fantasy series I've read is the Hall Family Chronicles by Jane Langton. Langton's books have more in common with the books of E. Nesbit and Edward Eager, which feature ordinary children in extraordinary circumstances, than with the works of Diana Wynne Jones and J. K. Rowling, which take place in elaborate alternate realities. Beyond this, there isn't really any way to compare the Hall Family Chronicles to other, better-known fantasy series. They are amongst some of the most unique, thought-provoking books for either children or adults that I have ever read.
The first book in the series, The Diamond in the Window, features siblings Eddy and Eleanor Hall, who live in a ramshackle old house in Concord, Massachusetts with their Aunt Lily and Uncle Freddy. Eddy and Eleanor love their home, but not everyone in the neighborhood feels the same way. Local banker Mr. Preek hates the sight of the house's turrets and stained glass amongst the neat little saltboxes on Walden Street, and schemes to have the house foreclosed upon and knocked down.
The fantastic part of the novel begins when Eddy and Eleanor take up residence in a secret room in their home's attic. The room used to belong to their Uncle Ned and Aunt Nora, who lived in the house as children. Ned and Nora disappeared one night in mysterious circumstances, causing Aunt Lily and Uncle Freddy to lock up their attic bedroom for years. Eddy and Eleanor insist upon moving into the room and soon uncover clues to a treasure hunt scattered throughout the room--a hunt that takes place at night in dream worlds the children visit while asleep. Unlike in ordinary dreams, the injuries the children sustain in these dream worlds carry over into the waking world. Could this explain what happened to Ned and Nora all those years ago?
What makes The Diamond in the Window so unique is the number of literary, philosophical, and cultural topics Langton touches upon throughout the course of the story. Uncle Freddy is a scholar of transcendentalism, a philosophy that was popular in New England during the 1830's and '40s, and was friends with a like-minded maharajah named Prince Krishna prior to Ned and Nora's disappearance. Langton makes numerous references to authors Ralph Waldo Emerson and Henry David Thoreau, two prominent figures in the transcendental movement. One adventure even finds Eddy and Eleanor inside the home of Louisa May Alcott, author of Little Women and daughter of transcendentalist Amos Bronson Alcott.
These philosophical concepts and other weighty issues are present in the seven other books in the Hall Family Chronicles. For example, The Astonishing Stereoscope focuses on religious beliefs throughout time and around the world, The Fragile Flag tackles political protest, and The Mysterious Circus and The Dragon Tree touch on environmentalism and preserving nature. While these themes can be difficult for children to grasp, Langton does an excellent job of making them appropriate and understandable for her audience. Furthermore, the philosophical aspects of the books never overwhelm the fantasy and fun of the plots.
If you're looking for something truly different to read, I couldn't recommend the Hall Family Chronicles more highly.