Thalli's sole purpose in life is to play music. In fact, everyone in the community is assigned a job early on. Scientists, of course, being top of the line -- as they are the only one's allowed in private areas and have the responsibility to apply the rules the others must obey. It is a post-apocalyptic state after all. If anyone can save the world, it's the scientists. To assure themselves that no other war will ever destroy the planet again, the scientists abolish feelings, so when Thalli is caught crying she is instantly plagued as an anomaly and must therefore fight for her life.
When John, Thalli's friend, tells her about a Designer who is bigger than the scientists and "puts us in seemingly impossible situations to demonstrate his power," I feared the whole book would be centered on a battle of faith vs. science. But instead McGee rolled up her sleeves and wrote a much more complex story filled with action, plot twists, and betrayal that steered away from cliches.
Thalli isn't always a strong female lead. She can be naive, obstinate that there is no Designer -- because he doesn't show up and saves us when we need him to -- allowing us to see our own vulnerability through hers.
My only concern is that the book had so many plot twists forcing the end to feel uncertain. After all, it is an open ending that hints at a sequel. I had to read it twice to make certain that I wasn't the one being conned.