from Jane Austen: A Life, by Claire Tomalin:

"An amazing horrid book," Austen made Isabella Thrope call [Samuel Richardson's] Sir Charles Grandison in Northanger Abbey, giving herself away in those four words, since it was Austen's favourite. "Her knowledge of Richardson's works was such as no one is likely to again acquire," wrote her nephew in his Memior, going on to say that every incident in it was familiar to her, and every character like a friend. A book so important to her, and now so little known, is worth some attention. (p. 71)