The Morgan Library in New York is hosting a marvelous exhibit
of Jane Austen's letters (The Morgan has what is probably the best and largest single repository of Austen's letters), the manuscript of Lady Susan, the only holograph Austen manuscript extant, as well as a collection of books and images that shed light on Austen's life and works.
There's a Flash-based online digital facsimile of Lady Susan as part of The Morgan's exhibit. Lady Susan is perhaps the least well-known of Austen's works. It's a short epistolary novel that she never submitted to publishers, and that she created in her early years, and later revised. It describes, in frequently satiric tones, the efforts of the widowed Lady Susan to find appropriate husbands for herself and her daughter. Lady Susan is a managing mother with a shy daughter, and a duplicitous nature—all of which is revealed, quite amusingly, through her correspondence. She is not, at all, a nice woman, but Austen's depiction of her is at points both brutally honest, and exceedingly amusing—particularly since Lady Susan is much more closer to the historic social reality than conventional manners of the time would admit.
You can read Lady Susan for yourself via the Gutenberg project as a free ebook. Lady Susan—and the rest of Austen's works—are also available as free ebooks at Feedbooks.

