So, the novels mentioned in Northanger Abbey -
The Mysteries of Udolpho by Ann Radcliffe
(this book is not actually one of the 7 'horrid' novels mentioned by Isabella to Catherine but it is a book that they read)
Trapped in a gloomy medieval fortress, an orphaned heroine battles the devious schemes of her guardians as well as her own pensive visions and melancholy fancies....
The Castle of Wolfenbach: A German Story by Eliza Parsons
Matilda Weimar flees her lecherous and incestuous uncle and seeks refuge in the ancient Castle of Wolfenbach. Among the castle's abandoned chambers, Matilda will discover the horrifying mystery of the missing Countess of Wolfenbach. But when her uncle tracks her down, can she escape his despicable intentions?
Clermont by Regina Maria Roche
Clermont is the story of Madeline, a porcelain doll of a Gothic heroine, who lives in seclusion from society with her father, Clermont, whose past is shrouded in mystery. One stormy night, their solitude is interrupted by a benighted traveller, a Countess who turns out to be a friend from Clermont's past.
Madeline goes to live with the Countess to receive her education, but her new idyllic life soon turns into a shocking nightmare. Ruffians attack the gentle Countess, and Madeline is assaulted in a gloomy crypt. And to make matters worse, a sinister stranger appears, threatening to reveal the bloody truth of Clermont's past unless Madeline marries him. Can she avoid the snares of her wily pursuers, solve the mystery of her father's past, and win the love of her dear De Sevignie?
The Mysterious Warning by Eliza Parsons
The good old Count Renaud is dead, and his will makes the degenerate Rhodophil his heir, disinheriting his other son Ferdinand, who has married against his father's wishes. Rhodophil promises to share his new riches with his younger brother and his wife Claudina, but Ferdinand hears a mysterious voice from beyond the grave, warning him to flee his brother and his wife to save himself from sin and death!
Ferdinand obeys the supernatural warning and sets out to find fortune and adventure. In the course of his quest he will encounter a recluse in a ruined castle with a horrible secret, find himself captured and imprisoned by the Turkish army, and encounter one of Gothic literature's most depraved female characters, the monstrous Fatima. And if he survives all these dangers, Ferdinand must return to Renaud Castle to solve the mystery of the ghostly voice and uncover the terrible truth about his wife and his brother!
I don't know about you guys but I am loving the sound of these. I supposes Counts back then are the same as Dukes today in fictions, there seems to be a surplus of them ;)