Every sentence she wrote was incredibly clever, witty and wise. I recommend Persuasion as the best of her novels. Harold Bloom called it the perfect novel. For me, it is what is in the back of my mind when I am writing, as the perfect build up of anticipation and then completion in a plot. I've read it at least 6 times and each time it is just as satisfying, except that I am always sad to finish.
There's a reason they keep remaking her books into movies. Austen is the expert at complicated plotting that looks simple. Her language is extraordinarily tuned, each character has his or her own 'voice'. Although she wrote about a limited social group (mostly 'middle-class' women getting married) her writing transcends the genre and still rings true today.