1. The book deals with subjects that probably aren't appropriate for elementary age children. While not graphic in any way, a good reading of the book requires more of a sophisticated understanding of human development in order for it to make sense. When Jonas has a proto-sexual dream, he is told that he has experienced The Stirrings and it's time to begin his "treatment" which comes in the form of a daily pill meant to inhibit The Stirrings.
Further into the story, Jonas discovers that Release from the community is not a form of exile into another community, but is premeditated execution/death. He becomes enlightened of this fact by watching his father Release an infant; a disturbing scene, not because it is graphic but merely because of the sinister implications.
2. The book is very Logan's Runnish/Brave New Worldish. A future Utopia is achieved by carefully controlling all aspects of society, from birth to death.
3. The book is not a great representation of the sci-fi genre. It takes place in the future. It presumes all sorts of technical advances, but not much detail is put into these features and they are not carefully thought out.
Debra Doyle, a young adult fiction author, hits the nail on the head with this criticism:
Things are the way they are (in the novel) because The Author is Making A Point; things work out the way they do because The Author's Point Requires It."
She's right, but I think that only more sophisticated readers would be bothered by it to the point of distraction.
4. I found the ideas about communal memories probably the most intriguing part of the book. In The Giver, there is one person who holds all the memories that have ever existed. The rest of the community don't possess these memories of pain, war, starvation...and also happiness, individuality, differences in the way things are and the way things used to be. The Receiver/The Giver is the only person who hold this inner knowledge within themselves. They bear the burden of knowing the freedoms and joys that have been lost along with the pain and difficulties that have been banished.
The memories separate them from everyone else and place them in psychological isolation in the community.
While not being the only theme Lowry develops, it is the one I found most "true". Having knowledge of awful things that other people don't know about is very isolating. Not sharing that knowledge in order to protect others is a heavy burden.
It hit home for me because I have known things about many people that I have never shared because of how it would affect others. Either through chance, confession, or accurate intuition, many secrets have rolled into my path, many of which I'd like to be blissfully ignorant. None of them are earth-shattering, especially if you happen to be fairly cynical internally. Yet there are times when it would be nice to "un-know" some things.
But I guess that's what the whole "knowledge of good and evil" theme is about in Genesis.
There is no "un-knowing" available.