A book that helped me understand what's going on in Austen the best was titled "Jane Austen and the Fiction of Her Time". Jane Austen loved novels, but was also dissatisfied with what she saw as the flaws of a lot of the novels around her -- both in the plots (unrealistic situations or unrealistic characters), and with the message they were trying to present. So many of the situations are direct allusions to other novels, and many of the main messages are subtle and subversive.

One of the things pointed out about Mansfield Park is that although all ends well for the main characters, it's basically by accident. If Henry Crawford had just gone back to check on his steward, as he knew he should have, he never would have been snubbed by Julia; would never have been tempted by wounded vanity to win her back; would never have run off with her, putting himself completely out of Fanny's reach; and would, in the author's estimation, have won her over eventually. And if Henry hadn't run off with Julia, Mary would never have exposed her lack of principles to Edmund, and they would have been married shortly too.