Life As We Knew It is a young adult science fiction novel by American author Susan Beth Pfeffer, first published in 2006 by Harcourt Books.

The book follows a teenage girl named Miranda and her family, who live in northeastern Pennsylvania and struggle to survive after an asteroid hits the Moon and brings it closer to Earth.

Miranda is a 16-year-old girl who lives in Pennsylvania with her mother, Laura, and her brothers Matt and Jonny, with her worrying about her grades and becoming a godmother to her half-sibling, who her father and his second wife, Lisa, are expecting.

However, the asteroid is denser than scientists expected, and soon after the impact, it becomes clear that it has pushed the Moon closer to Earth, intensifying the tidal forces that it exerts on it.

While they are safe from tsunamis because they live inland, during the summer tidal forces push magma to the surface and several dormant volcanoes erupt, filling the sky with ash.

During winter, the family also deals with snow and a lack of running water, natural gas, or electricity as an outbreak of influenza spreads through town and kills many people, including Peter, a doctor whom Laura was in a relationship with.

Miranda finds the post office abandoned, and as she is about to let the cold kill her, she notices a yellow piece of paper that leads her to the town hall, where the mayor is handing out bags of food.

With a renewed will to live, on her seventeenth birthday Miranda reflects on why she keeps a diary, wondering if it is for the people who might read it in the future or for herself, to help her process life.

Dr. Peter Elliot: Laura's boyfriend, who works as a doctor and visits the Evans several times, sometimes bringing food and giving medical advice.

Brandon Erlich: An ice skater from the town who is training for the Olympics and whom Miranda later meets at a frozen lake, where they talk and skate together.

By telling his congregation that God will sustain them and behaving in a falsely caring manner, he ensures that they will bring him food, which angers Miranda.

Kirkus Reviews said that "death is a constant threat, and Pfeffer instills despair right to the end but is cognizant to provide a ray of hope with a promising conclusion.