This recommendation is sort of ridiculous in its obviousness, but I suppose I shouldn't take for granted that everyone has read Jane Austen. I hadn't until just a few years ago -- I had to read plenty in high school, but never her, and in college I almost took an English class devoted to her but I had to drop it because the rigorous reading schedule would interfere with my ability to finish my thesis. That was the right decision (Highest Honors baby!) but I still think about that class and how much I KNOW I would've loved it.
After college I made it a specific and deliberate goal to read each of her complete, published novels, in chronological order or publication. That makes it sound like a chore, but it wasn't in the slightest. It was a delight, and when it was complete I couldn't wait to start again. In the interim, I've re-read my favorites and consumed a healthy amount of Austen biographies and criticism. I once had to do a presentation on digital strategies in archives at the University of Michigan, and I used Jane Austen's archival collections as my exclusive example. Now i've reached the point of enjoying reading about Jane Austen almost as much as I enjoy reading the novels themselves.
Paula Byrne has some great literary biographies under her belt (Evelyn Waugh comes to mind), but her most recent is The Real Jane Austen: A Life in Small Things. I highly recommend as a companion piece What Matters in Jane Austen by John Mullan for its thoroughness and insights into historical and contextual details. He dissects the names of all the female characters, for example, and parses out what we can assume about their personalities (hint: flashy, feminine names are usually bad). It really enriches her novels. A Jane Austen Education is a nice exploration of the six major novels by a male reader, William Deresiewicz, although I found his constant insertion (no pun intended) of masculine identity issues to be tiresome. His perspective is somewhere along the lines of "I think these books are good and I'm a man, so you know they must really be good." But, it was still a good read and his textual analysis is spot-on; he is a bit of an obnoxious man, but he's still a legit literary critic. For those who want to go full-on academic with it, there is no better volume than The Cambridge Companion to Jane Austen, which culls some of the very best writing on her work. If you enjoyed The Madwoman in the Attic, this is your best bet.
I'm anxious to get my hands on a collection of the letters of Jane Austen because her personal writing sparkles with as much wit as her novels and I'm getting to the point of having long passages of her novels memorized. I hope I'm not doomed to become one of those women who dresses up in Regency garb and makes pilgrimages to her hometown. Now is probably not the time or the place to get into a deep analysis of every Jane Austen film adaptation ever made, but just know that I could.