Book Twenty-Three is the penultimate book of the Odyssey. Odysseus has survived his many trials and made it home to Ithaca, killed the suitors who had taken over his household, and been reunited with his family. His reunion with Penelope is the final step he must take to complete his homecoming. Odysseus conceals his identity from his wife until after dispatching the suitors, which enables him to return to Penelope's arms as the undisputed lord and master of his household.
Penelope is overjoyed to welcome Odysseus home, and is eager to know what has happened to him in their long separation from each other. Odysseus recounts his experiences to her as they lie in bed together for the first time in twenty years:
of what hard blows he had dealt out to others
and of what blows he had taken—all that story.
She could not close her eyes till all was told.
A lot of things have happened during their time apart from each other. Odysseus takes action to undo the situation that has arisen in his absence, for he cannot truly return home while the suitors remain in situ. Penelope, for her part, needs to be able to "fill in the blank" of the past ten years. It is essential to Penelope to understand where her husband has been and what he has been through since the end of the Trojan War. They cannot move on with their life together until Penelope is privy to Odysseus's experiences.
For Homer's audience, this passage also serves as a "recap" of the events of the poem, signalling that the action is over now and the hero will rest from his adventures.
[Odysseus] drowsed over the story’s end. Sweet sleep
relaxed his limbs and his care-burdened breast.
Although Odysseus must fulfil one further obligation to discharge Poseidon's wrath, and although there is a temporary threat of violence in Book Twenty-Four, the main story of the Odyssey concludes with Book Twenty-Three, as Odysseus retells his story to his loving wife and then falls asleep in her arms.