When she wakes up, Liz Hall is dead. She doesn’t know it at the time. Just like she doesn’t know how she ended up in a room on a cruise ship with some stranger, a girl about her age sleeping in the next bed over. She doesn’t know where the ship is headed or why the captain is a seven-year-old boy.
It turns out she the ship is headed to a place called Elsewhere. This is the place you go when you die. It looks a like Earth. There are roads, houses, businesses, people, and pets. But there are some big differences too. Just like with our idea of Heaven, you will be reunited with people you know who died before you. Liz ends up seeing her grandmother. But you don’t stay in Elsewhere forever. Instead, you age backwards from the time you die until you are just seven days old when you are sent back to earth to be reborn as a totally different person.
Liz was only 15 when she died. That means that she will never graduate high school or college, become an adult, get married and have kids. She has to figure out how she will spend the next 15 years of her life.
Which is not to say that some of those things are not possible. There is a love story here but that is all I will say. To find out the rest, you will have to read the book.