Even though she has only a small role, Helen is one of the Iliad's most interesting characters. For one thing, she is supposed to be the most beautiful woman in the world... which we think is pretty interesting. (How can they tell? Have they seen all the women? What does she look like, exactly?)
Beyond that, though, Helen is notable for her conflicted attitude toward her Achaian origins and her new home in Troy. From Book 3, we get the sense that she thinks running off with Paris was a big mistake. (She even gets up in the goddess Aphrodite's face, blaming her for causing so many problems.)
From Book 6, we know that she doesn't think highly of Paris—and sense that she might have a bit of a crush on Hektor (though he has eyes only for Andromache). Book 24 reveals part of the origins of her feelings: Hektor was one of the few people in Troy who was nice to her. (Though she doesn't mention it at the time, she also has formed a bond with Priam, along father-daughter lines.) In the eyes of most Trojans, Helen means nothing but trouble.