Dr. Franklin's Island by Ann Halam (aka Gwyneth Jones) (Random House - Laurel Leaf)
Miranda and Semirah are stranded on a remote island following a plane crash. Unfortunately, that's just where a mad scientist has a lab--and is trying to turn people into animals and the other way around. The friendship between Miranda and Semirah as they struggle to escape and to stay themselves in an intricate one, allowing for readings on several levels. The mass market paperback includes an interesting discussion with the author on the various themes, from ethics to friendship, found within.