It's hard to know where to begin when talking about Ligeia. The narrator just tells us so much about her that it seems sort of unnecessary. Still, the thing that really sticks with you after all the talk isn't how smart or beautiful she is. It's that she can't really be described. The narrator spends pages and pages on her and yet he can't sum up her "expression." He's left recycling the quote that appears at the beginning of the story. It's as if he's just running in circles.
About that quote: the narrator tells us, after years of reflection, that he's been able to make "some remote connection" between the Glanvill passage and Ligeia. He identifies a certain shared intensity and passion – a passion and intensity that reveal themselves when she wills herself back to life at the story's end. (See "What's Up with the Epigraph?" for more on the Glanvill quote.)
Still, it's sort of strange that we don't really get to hear from Ligeia at all, at least not directly. We hear her quote Glanvill, sure, and she writes that poem – but both of those things are indirect communications. "OK," you say, "but actions speak louder than words, and she raised herself from the grave!" We'll give you that, but you have to admit – well, you don't have to, we guess – that the same thing that makes Ligeia so mysterious also makes her seem a little bit less powerful sometimes. Sure, she can possess a body and call forth mysterious drops of deadly liquid, but the lady can't even speak for herself.