The story has been adapted to the cinema much more often than "Berenice," but to make the narrative work in a film, it's usually dumbed down into a story of a dead mother's spirit possessing the living body of her daughter, which isn't even close to what happens.
In contrast, "Ligeia" is a more outright "ghost story," though still told in a more indirect than most works in the subgenre. In contrast to "Berenice," the narrator can't even remember when he first met the beautiful Ligeia, though as with "Morella," the thing the male character holds most in common with his lady fair is their mutual interest in occult studies. Yet this time Poe devotes a lot more time to discussing the many beautiful features of the mysterious female-- eyes, nose, chin-- and relates the total effect of Ligeia's loveliness to a quote by Francis Bacon that defines beauty in terms of its
Like both Morella and Berenice, Ligeia sickens and dies. However, like Berenice Ligeia has a conduit that will return her to the mortal world, and it's not anything as earthbound as mere catalepsy. Rather, her knowledge of occult philosophy suggests that she may be able to keep herself-- or maybe her spirit-- alive beyond death, or, as she calls it in her poem-within-the-story, "The Conqueror Worm."
Ligeia's body at least perishes in an unnamed city on the Rhine, after which the narrator-- who has inherited her great wealth-- travels to England and buys a deserted abbey, which he restores to become his new home, as he is taken with the "gloomy and dreary grandeur of the building." Where Poe devotes one long paragraph to descanting on the beauty of Ligeia, the abbey gets four full sections, suggesting that Poe is almost more interested in the tomb than in the womb.
Then, in what sounds very much like an arranged aristocratic marriage, the narrator marries an Englishwoman, Rowena. The two don't get along, and soon Rowena too is stricken by some unnamed illness. She comes near death, but rallies. It may be at this point that Ligeia's spirit-- at least in the more traditional ghost story-- begins to get a new toehold in the mortal world. After much buildup, Ligeia makes her presence known in one of the odder manifestations in horror-fiction, which may be something Poe derived from a secondary source.
It was then that I became distinctly aware of a gentle
footfall upon the carpet, and near the couch; and in a second
thereafter, as Rowena was in the act of raising the wine to her lips,
I saw, or may have dreamed that I saw, fall within the goblet, as if
from some invisible spring in the atmosphere of the room, three or
four large drops of a brilliant and ruby colored fluid. If this I saw
-- not so Rowena. She swallowed the wine unhesitatingly, and I
forbore to speak to her of a circumstance which must, after all, I
considered, have been but the suggestion of a vivid imagination,
rendered morbidly active by the terror of the lady, by the opium, and
by the hour.
Yet I cannot conceal it from my own perception that, immediately
subsequent to the fall of the ruby-drops, a rapid change for the
worse took place in the disorder of my wife; so that, on the third
subsequent night, the hands of her menials prepared her for the tomb,
and on the fourth, I sat alone, with her shrouded body, in that
fantastic chamber which had received her as my bride.
And then follows the big climax, in which Rowena's dead body comes to life, taking on the very appearance of Ligeia-- and there the story ends.
It's been suggested that the opium-addled narrator may be just imagining the whole thing. I can't deny that Poe leaves himself this "out." But prior to "Ligeia" the author shows no bashfulness in portraying the "real marvelous" in his tales: he's no Ann Radcliffe, seeking to dispel the fancies of ghosts and demons from spooky tales. I also think the average reader, both in Poe's time and this one, is likely to take the narrator as reliable on this score, given that the recrudescence of Ligeia is a thing about which said narrator is justly ambivalent.