This is a book for older children or you YA readers. It is based on a real historical event, where a native-american woman was abandoned on an island for 18 years. The book, in the style it is written is far ahead of its time. It could be published today, and would fit right in in modern writing.
It is an easy and enjoyable read, which is good for children. It has relatively little to offer the adult reader, because it does not really work on multiple levels, although it is not boring. I don't think, that despite its innovations, that it really deserves its classic status, although there is nothing wrong with it, and it does manage to both effectively convey the brutality and beauty of nature.