I haven't read
The Giver, but those who have say it works as a standalone novel even though it's part of a series, much like
A Wrinkle in Time can be read as a standalone even though it's also part of a series.
Here are some links for
The Giver:
Amazon US:
http://www.amazon.com/The-Giver-Quar...dp/B003MC5N28/
Barnes & Noble:
http://www.barnesandnoble.com/w/give...=9780547345901
Kobo:
http://www.kobobooks.com/ebook/The-G...IDg/page1.html