How to tell you're reading a gothic novel – in pictures

When Horace Walpole published his 'gothic story' The Castle of Otranto, he launched a literary movement which has sired monsters, unleashed lightning and put damsels in distress for 250 years. A horde of sub-genres has followed, from southern gothic to gothic SF, but are some novels more gothic than others? We return to the genre's roots in the 18th century for this definitive guide