Ruins by Orson Scott Card is the second book in the Pathfinder series. In this book Rigg, a 15 year old boy that can see paths and go into the past, and his friends live on a planet called Garden. On Garden there are 19 colonies and each has an invisible wall that is impossible to pass. By going into the past, Rigg and his friends find a way to pass through the wall.
  
On the other side they find out that the people in this colony have found out that the world is going to be blown up by the people from Earth in three years. Rigg and his friends then decide that they should try to stop the people from blowing up their planet. The rest of the book is about the group trying to save their world. 

One big problem I had with this book was how confusing some scenes were. In the book they talk a lot about time travel and it doesn't make any sense. Here's an example, "During the microseconds when the ship's nineteen computers were separately calculating and activating the jump." There are whole pages where they talk about stuff like this.     

I thought that this book was o.k. Most of the book didn't have a lot of action and was kind of boring. I feel like the author went way too slow and this book could have been a lot better if it was faster paced. However, the last 100 pages were fast paced and action packed. Also there were tons of mini cliffhangers that kept the book interesting. So for these reasons I'm giving it a B minus.