Hugoâ s novels as well as his plays have been a great source of inspiration for musicians , stirring them to create not only opera and ballet but musical theater such as Notre-Dame de Paris and the ever-popular Les MisÃ rables , London West Endâ s longest running musical . Hugo 's novels as well as his plays have been a great source of inspiration for musicians , stirring them to create not only opera and ballet but musical theater such as Notre-Dame de Paris and the ever-popular Les MisÃ rables , London West End 's longest running musical .