I've talked before about how The History of Sir Charles Grandison is the one novel we know Catherine has read before she is introduced to the Gothic novels, but now I've got to vent some feelings about John Thorpes literary tastes.
He says that Radcliffe's novels are "amusing enough" (without knowing which books she actually wrote) but he explicitly states: "Novels are all so full of nonsense and stuff; there has not been a tolerably decent one come out since Tom Jones, except The Monk;" Now I doubt the significance of these books is anything new to people who study English literature, but finding it out was like a cool Easter egg to me, so I'm gonna blab about it:
At first glance these are excellent books for a guy like Thorpe to brag about liking, because there is basically only one thing that unites them: sexual content. The History of Tom Jones, a Foundling by Henry Fielding, is a "rake reformed" narrative, while The Monk is a Gothic novel deliberately filled with depravity, ending in eternal damnation. They're completely different kinds of books and regardless of how good they may be, neither ought to be talked up to a nice young lady you've only just been introduced to.
But considering Austen's love for literature, this choice of authors was probably equally deliberate. Just to show off that Thorpe's tastes are incompatible with Catherine's. (And cannot hold a candle to Henry Tilney's, who loves Mrs Radcliffe's novels.) Because...
• Henry Fielding, writer of Tom Jones, was the main literary rival of Samuel Richardson, who wrote Sir Charles Grandison. The latter wrote "Pamela; or, Virtue Rewarded", the former responded with the parody "An Apology for the Life of Mrs Shamela Andrews". They were both pioneers of the English novel, but wrote very different types of stories with very different moral tones (x, y). At this point of the novel we already know that Catherine likes Sir Charles Grandison (while Isabella expresses surprise at her being able to get through it), so making Thorpe like Tom Jones feels almost like a wink at the reader.
• Then there's the mention of The Monk, which is even more significant in a story where the two leads love Ann Radcliffe. Because Matthew Gregory Lewis was at least partly inspired by The Mysteries of Udolpho when he began writing The Monk (a), and Ann Radcliffe was so dismayed by the book that she then wrote The Italian in response (b, c). Once again two literary rivals, one that Catherine is a fan of, and one who Thorpe prefers.
It's also notable that despite absolutely being part of the Gothic genre, The Monk is not on Isabella's list of novels to read with Catherine. Which makes it extra silly that my beloved Northanger Abbey (2007) adaptation not only has Catherine read The Monk, but also lets her fantasize about a scene that really really isn't sexy in context.
I do really encourage reading a summary of The Monk if you can stomach the mentions of sexual violence, however. Lewis wrote it when he was 19 and despite its popularity was rather embarrassed about it later in his life. And while it is full of satanic seduction and murder, someone also accidentally elopes with a ghost, which makes up for a lot.