I think Edith Wharton is one of the most under-rated female authors. Yes, she is a bit well-known and some of her novels appear on AP reading lists, but most people manage to get through high school and college without ever having read her work, and if The House of Mirth were a Henry James novel (which it kinda could be), it would be put up on a higher pedestal. I don't know what it is about Edith Wharton -- maybe because her novels are about the American upper classes, or maybe because she was herself an extraordinarily wealthy and independent woman, no one takes her as seriously as an author who struggled a bit more? Wharton was widely celebrated in her own time, but her work seems to have fallen out of favor over other American women writers of the same era who were more concerned with class struggle, racism, and the immigrant experience (Willa Cather, for example). If nothing else, she should be lauded as the proof of concept for Virginia Woolf's A Room of One's Own; as an independently wealthy woman with few domestic concerns, Wharton was a very productive and successful writer.
I started my reading relationship with her with Ethan Frome, which I have no desire to read again as a 27 year old, although I loved it when I was younger. It is spare and romantic, melodramatic and very heartbreaking, and a bit macabre in its ending. I am always inclined to recommend an author's shortest work to someone new to them, but in this case I wouldn't because although Ethan Frome is a satisfying and short read, it is not her best work, nor is it most representative of her style. Fans of marriage plot novels that are doomed from the start (Wuthering Heights) will probably enjoy this immensely.
The Age of Innocence is probably her best-known and most celebrated novel, and for good reason. It is also my personal favorite, and was so ahead of its time in its portrayal of gender dynamics and roles. It is essentially a marriage plot novel that plays out Manhattan's upper classes in the late nineteenth century. What separates it from the pack of marriage plot novels of this era is that our romantic heroine in this case is a hero, Newland Archer, whose impending marriage veers off course with the arrival the Countess Ellen Olenska. Newland is an utterly fantastic character. and it is really striking how feminine he is allowed to be. The novel is essentially 300 pages of his feelings, but it never steers into terrible German Romanticism (Sorrows of Young Werther, one of my least favorite books of all time).
The excellence of the Age of Innocence is only reinforced by the beautiful 1993 film adaptation by Martin Scorsese. It is a very faithful and carefully crafted adaptation, with Daniel Day Lewis playing Newland Archer.
The House of Mirth is the other big, significant Wharton novel, and it follows the endlessly frustrating and fruitless struggles of 1890s bachelorette Lily Bart, who has money and class, but never enough. Other than the fact that the reader will inevitably want to strangle Lily at every turning-point in the novel, it is an engrossing and witty read. I like to imagine Lily Bart meeting Catherine Sloper of Henry James' Washington Square. Based on geography and chronology, they could have been neighbors and run in the same social circles, but they are such vastly different women, and I can't even imagine the conversations they could have about love, wealth, and marriage.
As you can see from my photo, I also have a biography of Edith Wharton by Hermione Lee. Wharton's own life was as interesting as that of any of her characters, if not more so. She spent much of her time traveling and having adventures, breaking hearts and writing novels, so if you enjoy her work, you'll enjoy this very satisfying and meaty biography of her as well.