2nd weekly update on Emma progress and other musings

My favorite of the three Emma movies I've seen is this one. 

After nearly a year of slowly, oh so slowly, reading the book Emma by Jane Austen I've decided that I'd best find a way to encourage myself to actually complete it. Thus, this weekly update is born. Once a week I shall report on my progress, pose a question or two, reflect on anything and everything Austen.

Weekly progress: Part 3, Chapters 1-12; pages 285-379.

50 page goal reached? Yes, plus some. At one point my momentum was so good the thought occurred that I might actually finish the book this week. Alas, that is not the case.

Current action: Up to this point in the book there hasn't been much action, but with the start of Part 3 things pick up. First, with Frank Churchill back in the near neighborhood, the Westons can now host their ball at long last. Emma determines that she isn't in love with Frank but decides that Miss Smith is just the gal for him. Later Mr. Knightley hosts a strawberry party and the very next day Emma leads a trip to Box Hill and then acts very badly to her guests. Mr. Knightly calls her out causing Emma to feel deeply grieved. Mr. Knightly abruptly leaves town. After he is gone Miss Smith makes a revelation which causes Emma to realize that she is in love with him but she fears that her behavior has chased him away forever. While he is gone there is some big news about Frank and Miss Fairfax that shocks everyone.

Surprises: After the outing to Box Hill broke up badly and everyone went home, Mrs. Elton hosted a party at her house in the evening and invited everyone but Emma (and presumably, Harriet Smith.) Mr. Knightly didn't attend, however, and everyone was pretty tired from the earlier outing so the party wasn't much fun. Ouch! That must have hurt Emma's feelings but in her contrite frame of mind when she learned of this from Miss Bates, she didn't appear to be upset by the obvious slight.

Questions: Why did Jane Austen leaves so much of the action to this last section of the book after so little in the first two sections?

Comment: I am now almost 99% certain that I've never read Emma before, unless you count flipping to the good parts and reading/rereading them. I know I've read Pride and Prejudice, Persuasion, and Northanger Abbey but now I am having my doubts if I've ever read all of Sense and Sensibility and any of Mansfield Park. I've just seen the movies so many times I feel like I have. After discovering all the things the movies leave out, I am now determined to read the last two books I mentioned in their entirety once I'm done with Emma. (Which I realize is a pretty ironic thing for me to say on the heel of confessing that it has taken me over a year to read Emma.)