The TV adaptation delves more into Marianne's semi-serious college relationship with the popular debater Gareth and their break-up (which was relatively non-climactic). In the novel, however, we don't really see much of her with Gareth — he's only really mentioned at the party where he introduces Connell to Marianne. Several months after they meet again, Connell and Marianne simply begin to casually date after hooking up.