Amy is being cryogenically frozen so that 300 years later, she'll wake up on a new planet called Centauri Earth, where Sol Earth (or our Earth) has discovered evidence that might suggest a habitable world. She's labeled as unnecessary cargo, boarding the spaceship called Godspeed only because her mother is an expert in biology and her father an officer for the military. But something goes wrong, and she finds herself waking up fifty years before Godspeed is supposed to land.
While Amy was sleeping in her cryo chamber, however, people thrived outside. Generation after generation were born on the ship, serving for Godspeed until the one day it would land among the terrain of Centuari Earth. But something horrible, called the Plague, caused hundreds of these people to die, and a new system of leadership sprang up. Now, the ship is controlled by an Eldest, from which an apprentice called an Elder will take over when he dies, and so on and so forth. When Amy wakes up, she finds that everything is different-the people on this ship have rewritten history, have manipulated the very DNA of every human on Godspeed, hoping for unlimited control. And when she meets Elder, the expecting Eldest, she's not expecting a boy her own age, a boy she's finding herself attracted to...
Across the Universe was okay in every aspect. The characters were not flat but not dynamic either, and the writing had neither beautiful prose nor was too childish. The plot was very slow in some parts and was a bit predictable. Everything to be revealed probably occured in the last few pages of Across the Universe, which was too long a wait for me, and by the end, I was getting truly tired. The thing that really irritated me was that they never actually reached the planet, which I was really hoping for. After watching Avatar recently after finishing Across the Universe, I realized the two had similar set-ups, though they had totally different ways of going at it, and I imagined that their must've been tons of material really close to Across the Universe out there in plot.
The way Across the Universe ends doesn't really call for a sequel. Everything is kind of concluded and tied up, but I wouldn't be surprised if there will be one. Either way, I'd be excited to learn more about Amy and Elder after the aftermath in Across the Universe.