Here is an excerpt from a review about Lois Lowry's The Giver. I have only included the analysis of the ending. Use the web citation for the entire critical analysis.
Lowry's ending, though ambiguous, lends support to the idea that the novel embraces wholeness as a healing principle. In the end, Jonas, who has run away from home with Gabriel in tow, discovers a place that he remembers. He finds a sled that he remembers, mounts it, and its runners slice through the snow and take him towards Elsewhere, the place that holds his and Gabriel's future and ... past. Jonas then hears music for the first time. He is able to hear the music, to recognize the music, because he has relinquished others' memories, and in so doing has opened the door to his own perceptions. It is now possible for his new thoughts and feelings to join with his old thoughts and feelings. Lowry foreshadows this perplexing but hopeful ending when she describes Jonas as Keeper of the memories of the whole world. Her message, finally, is that one cannot ignore uncomfortable memories; one must embrace a whole vision, which contains joy as well as pain, if one (or one's children) is/are ever to feel at home in the world.
Though Lowry has consistently declined to interpret The Giver's ending, she has revealed that she is pleased by young readers who have perceived the magic of the circular journey, and the truth that we go out and come back, and that what we come back to is changed, and so are we.