4 ideas
In their final year at a Sligo school, popular working-class Connell, whose mother cleans the house of wealthy, isolated Marianne, begins a secret sexual relationship with her that he hides from his friends. He then asks another girl to the debs, and Marianne leaves school. The injury, caused by his fear of social judgment rather than by any lack of feeling, shapes their relationship for years.
Status depends on the setting rather than the person. At school Connell is admired and Marianne is scorned, but at Trinity her money, confidence and cultural fluency make her socially central while he feels provincial and out of place. Each person's self-worth is tied to whichever hierarchy currently surrounds them, so a shift in setting can reverse who holds power between them.
The couple's repeated breakups come mostly from things neither says, not from open conflict. The clearest case is Connell being too ashamed of his money trouble to ask Marianne if he can stay with her for the summer, which she reads as him ending things. Pride, class shame and fear of seeming needy make each person guess at the other's meaning, and the wrong guesses harden into separations.
The novel shows two people changing each other through sustained attention: Connell gives Marianne a sense that she deserves tenderness, and Marianne gives Connell the ambition and inner permission to pursue writing and a life outside Sligo. Love here works less as a union than as a way for each person to become more fully themselves. That is why the ending can treat separating for his opportunity in New York as a form of love rather than its failure.