The Giver is a coming of age novel because it is about a boy’s realization of what his world really is and what he does about it.
At first glance, Jonas’s world seems perfect. In fact, Jonas was raised not to question things. As the theme page notes:
A key characteristic of the particular community Lowry has created is the annual ritual in December when each year group, en masse, is declared one year older and given commensurate privileges and/or responsibilities. (enotes themes, The Giver)
It is at this ceremony that Jonas becomes the new Receiver of Memory and comes to know more about his community. Before becoming Receiver, Jonas questions nothing. He accepts things as they are. As he comes to learn more, he begins to question. He lies to his parents for the first time about how he really feels. He asks to see the video of the release ceremony of the newborn twin. At that point, everything changes.
wore. It was possible, what they had planned. Barely possible. If it failed, he would very likely be killed. But what did that matter? If he stayed, his life was no longer worth living.(p. 155)
Jonas grows and matures over the course of the book and his time with The Giver, but this is the instant when he faces reality. He realizes that the community is not a haven, and terrible things are happening there. He takes action, and rescues baby Gabe, at the same time returning the memories to the people so they can feel.
Lowry, Lois (1993-04-26). The Giver (Newbery Medal Book) (p. 155). Houghton Mifflin Harcourt. Kindle Edition.