You could think about what sort of storytelling occurs in both texts e.g. in "Ransom", there's Achilles' memory of the arrival of Patroclus, Priam's story about his childhood as Podarces and the "chance" that gave him back his position as king. There's also Somax's story about his family, In "Invictus" Mandela refers to his time on Robben Island, but there's also Eastwood's cinematic "storytelling" of the Springboks progress to become World Cup winners. Another type of storytelling is in the "newsreel" style introduction to Mandela's rise to become President. Think about what these different styles of storytelling can convey - some are used to compress events and give the audience important background knowledge, some are used to highlight turning points in the life of particular characters. Some will convey inner thoughts and emotional responses (like Somax's stories about his family). Some of these stories may also have a symbolic importance (I think the focus on the rugby at the end of the film is a kind of reflection of the South African struggle for unity - Eastwood doesn't show you the demonstrations, riots and shootings, he shows you the "combat" of rugby instead). I hope these comments are helpful for giving you a start with this topic.