Robert Louis Stevenson 
The strange case of Dr. Jekyll and Mr. Hyde [EPUB ebook] 

Strange Case of Dr Jekyll and Mr. Hyde" is a gothic novel by the Scottish Robert Louis Stevenson. The novel tells of a London lawyer named Gabriel John Utterson who investigates strange events between his old friend, Dr. Henry Jekyll, and the evil Edward Hyde. The impact of the novel is such that it has become a part of the language, with the same phrase "Jekyll and Hyde" which is going to mean a person who is very different from the moral point of view from one situation to another.