The book is a short novel that Charlotte wrote when she was just 18, long before she published anything. The main characters and setting are from Angria, the fantasy world she and her brother Branwell created and wrote primarily about.
The manuscript had been bound with two others of Charlotte's early pieces, presumably by an early collector of Brontëana, and was not discovered until 1892, when it surfaced in a used bookstore in Brussels. Almost forty years later, it was published by the Oxford University Press.
I had a difficult time with the book, because of all the alternative names for characters (just like the author of the introduction said some readers do), and I think I would understand it better in a second reading. However, it was also very interesting to me to read an early, unpublished work by one of my favorite authors, and see both the similarities and the differences from her later (published) novels.