Prenna wears coke bottle glasses, is extremely strong in physics, in love with the boy down the road, and she's from the future. When she is from, the world has been decimated by a terrible blood plague, the likes of which we have never seen before. 

In order to escape this disaster a group known as the travelers have taken it upon themselves to mooch off the past for protection from the future. Their only hope is that they will die before the plague begins...

This book was phenomenally written and I fell in love with the story just as swiftly as I did with the Sisterhood books. She knows how to turn a pretty word.