...a subgenre of romance novels set during the period of the British Regency (1811-1820) or early 19th century. Rather than simply being versions of contemporary romance stories transported to a historical setting, Regency romances are a distinct genre with their own stylistic conventions that derive from the works of Jane Austen (and to some extent from distinguished Austen progeny such as Georgette Heyer and Clare Darcy), and from the fiction genre known as the "novel of manners." In particular, the more traditional Regencies feature a great deal of intelligent, fast-paced dialogue between the protagonists.
I Capture the Castle, by Dodie Smith, and Pride and Prejudice, by Jane Austen. I understand the first reference, because, after all, they both take place in a draughty castle in a remote location, and in both books the fortunes of the family are dependent on the daughter of the family marrying someone wealthy; but it's really more of a Georgette Heyer homage, given its Regency trappings--the Dodie Smith book is set in the 1930s.
As for Pride and Prejudice, I imagine that was the one cited because it is more well known (and also because its heroine is similarly poverty-stricken), but in some respects this book reminds me more of Emma--an entirely clueless heroine bent on settling everyone's personal lives to her own self-satisfaction. Anarda also pointed out its possible similarity to A Brief History of Montmaray, by Michelle Cooper (which I reviewed here), and it does agree in some respects (crumbling castle, no visible means of support--the heroine, not the castle, although both are true!), but again, much closer to Georgette Heyer, though without the enduring qualities of her books.