Usa: conociendo libros (XIII)

GRAVITY by Melissa West (October 2012)

BLURB:
In the future, only one rule will matter:

Don't. Ever. Peek.

Seventeen-year-old Ari Alexander just broke that rule and saw the last
person she expected hovering above her bed - arrogant Jackson Locke, the
most popular boy in her school. She expects instant execution or some kind
of freak alien punishment, but instead, Jackson issues a challenge: help
him, or everyone on Earth will die.
Ari knows she should report him, but everything about Jackson makes her
question what she's been taught about his kind. And against her instincts,
she's falling for him. But Ari isn't just any girl, and Jackson wants more
than her attention. She¹s a military legacy who¹s been trained by her
father and exposed to war strategies and societal information no one can
know - especially an alien spy, like Jackson. Giving Jackson the
information he needs will betray her father and her country, but keeping
silent will start a war.

http://www.goodreads.com/book/show/12844575-gravity