] Does anyone know anything about this ‘amazing horrid book’ that Miss Andrews could not get through the first volume, but Mrs. Morland is so fond of?

Well, for one, JA was very fond of Richardson generally (no wonder, he was the first proponent of proto-psychological novel in English), and of Sir Charles Grandison in particular. Her nephew, J.E.Austen-Leigh, wrote in his Memoir, that JA knew well-nigh by heart "everything that took place in the cedar parlour". Richardson can miraculously be both voluminous and intense, though for the grip on readers perhaps Clarissa scored better. As to the hero itself, he is an upright and honourable (though occasionally dull) man, and served for the next century as the model, when a reader, full of sensibility, wanted to praise some young man. The novel (in 12 books, if I'm not mistaken) is full of incidence, but not of Gothic kind.