Son

After meandering around a few other side stories, the Giver series finally returns to the original story line in the conclusion. Son starts out in the same village as the Giver. We follow the story of a girl who became a birth mother. We gradually learn that she had lived at the same point in time as the Giver. She had a difficult birth and was then reassigned to a different job. However, in reassigning, they had forgotten to give her the "pills" that cut off emotion. She had the yearning to see her son, and eventually found him at the nurturing center. After he Jonas flees with baby Gabe, she ends up boarding a boat and ending up in another village. There she discovers a society vastly different from her own. (It somewhat resembles a somewhat primitive society with little technology, but a degree of learning and understanding.) From there, she builds up strength to climb out and find her son. Alas, she makes a great trade with the Trademaster and loses her youth in exchange for seeing him. She doesn't let him know until near the very end.
You could easily jump from the first book to this book in the Giver series. The two middle ones provide deeper understanding of the world, but are not really needed to follow these plot points. I would have been fine with the "Trademaster" being removed from the book. He seems to be added to allow a "superhero" conclusion where good triumps over evil. However, the supernatural abilities just don't fit well with the rest of the work.