It's an interesting thing to note, that if you go searching for information on Emma on the web, 90% of the hits you get will be aimed at kids. I'd assume high schoolers, since I wouldn't assign the book to younger readers myself, but still, questions like "How many characters marry in Emma?" make me cringe. I think the correct answer is, "All of them", more or less. Then there are the Austen online biographies, of which there are roughly three million. I don't know how much I'd have to wade through to get the answers I want, to the questions I have, none of which I can remember any more. The edition of the book I read wasn't annotated much better, either. We learn that "Imaginist" is a word Ms. Austen made up which means, "One who imagines", and that's great, but somehow I think I could have figured it out all on my own. On the other hand, every so often there is an allusion or maybe just something going on behind the scenes, that I'm sure was perfectly clear to every contemporary reader of the book, which left me saying, "Now what exactly did you mean by that?"
My favorite thing about reading these older books is the unconscious descriptions of the society. You can hear people saying, "Oh yes, back then women were practically forced to get married, they were always addressed as Mrs. or Miss, and they always took their husbands' names" but you don't really feel it until you read a book like Emma, where things like this aren't discussed, aren't mentioned, they simply permeate the book and the telling of the story. They are basic facts of existence Without Which One Could Not Exist. You don't get the same effect from reading a modern novel that is merely based in that time.
Anyway, it's a good book. You have to enjoy the "Novel of Manners", as I've heard them called; there is a surprising lack of car chases, death scenes, or even bank robberies; the point of the book is simply: how does one get what one wants in a society in which behavior is so strictly regulated? You soothe, you hint. You avoid ruffling feathers. At one point Emma is obliged to spend an afternoon with Mrs. Elton, whom she truly dislikes, in order that her degree of dislike not be known. (The utter uncouthness of Mrs. Elton simply cannot be described; she refers to her husband as "Mr. E", if you can imagine.) But once you get into the feel of thing, the lack of manners is truly grating. I think I'd prefer to bang my head against the wall rather than read over one of Mrs. Elton's obnoxious speeches again.
I'm not going over the plot. Google for "Jane Austen Emma" for many many descriptions - primarily in words of one syllable - and you'll find everything you need to know. It starts a bit slow, but by the time Emma has managed to get herself well and truly tangled in her attempts to matchmake for everyone around her, it's impossible to put down without finding out how she extricates herself. Read it. And always be polite.