Jane Austen herself once commented that she didn't think many people would like the title character. I can only assume that this is because Emma is a spoiled, self-important twit who thinks she knows everything... If you took the vapid, self-absorbed hotness of your least favorite high school cheerleader/model/actress, multiplied it by the know-it-all behavior of Hermione Granger from Harry Potter (minus the magic and scholarly pursuits) and divided THAT by the matchmaking prowess of Patti from T.V's Millionaire Matchmaker, you would have the character of Emma.
To make a really long story short: Emma is a meddling twit who credits herself for her sister getting married. This inspires her to try to set up a girl she befriends, Harriet, with a guy who is totally out of her league (Mr. Elton) while discouraging Harriet from marrying the guy who is in love with her and is totally perfect for her- all because he doesn't have enough money for Emma to think he's important. A good family friend who is also Emma's brother-in-law tries to tell Emma that her notions are totally whack, but she's too much of a dumb bitch to believe him. Mr. Elton turns out to be a total dick who wants to marry Emma for her money, thus Harriet's stupid little heart (nice girl, but kind of a moron) gets broken. Mr. Elton instead marries an even bigger twit than Emma, and everyone with half an ounce of sense wants to punch her face in; but no one does because it's England and they all have exceptional manners and sexy accents. A whole bunch of people who have no bearing on the body of the story weave in and out of the picture doing random B.S. and it turns out that two of them were secretly engaged the whole time (oh, snap!) and it creates a scandal and a lot of embarrassment because everyone has too good of manners and too much free time. Harriet decides she has the hots for Emma's brother-in-law because he was nice to her, and that makes Emma realize that she's totally in love with him. Turns out he's been in love with her since she was 13 (eeeeew, CREEEEPY!!!!) and poor Harriet gets screwed over again. Then the guy who wasn't 'good enough' for Harriet comes back into the picture, and she decides that she loves him no matter what Emma thinks- which is super convenient because Emma eventually realizes that she is a spoiled, self-important twit and has a major change of heart. Everyone gets married and lives happily ever after, and by the end of the book you no longer want to beat Emma's head in.
