When everyone heads outside one evening to look at an asteroid striking the moon, no one imagines the aftermath. The first book in the series is Miranda's diary. A fairly typical suburban teen, her entries about prom dresses quickly turns to wondering if she'll ever see her father again, or when her family will run out of food.
The second book in the series is The Dead and the Gone. It takes place at the same time, but the story becomes much grittier. Alex's parents are not at home, and likely didn't survive the immediate horrors of the asteroid's effects on earth. He is left to protect his sisters on the streets of Manhattan, where anything-or anyone-can be traded for food or water.
The third book, This World We Live In, brings Miranda and Alex together. It's the weakest of the series, but readers generally plow through it to find out what happens to these realisticaly portrayed teens.
The fourth book, The Shade of the Moon, received very uneven reviews. Readers want desperately to find out what happens with Miranda, Alex and their families, but many readers are disappointed with the ending. Of course, so were readers of Mockingjay! Reading the first book, or first two is perfectly OK for students who can live with ambiguous endings.