Let me give it to you straight, this book is fantastic! It starts off when Harry Keller a High School boy learns that he can go into another dimension called A-Time. In A-Time he can see people time lines: the past, present, and future of people and the different choices they make. Everything is going great in A-time when he discovers creatures that he calls Quirks. Quirks are bad events in time that try to force their way into people's time lines. Most of the unfortunates events are minor for instance, drop your mail or have a cramp in your leg but Harry finds a huge Quirk, a suicidal Quirk on Todd Penderwhistle's future time line. On top of all of this, Harry is faced with a huge conflict in his own life- the same boy, Todd threatened to kill Harry earlier that morning. Harry is faced with a decision- Will he use his power to save his enemy Todd, or just say "Well that's too bad for him." This book is fast paced and keeps you on the edge of your seat during the entire novel. The author, Stefan Petrucha (who has written many popular books including some of the Nancy Drew series) does a phenomenal job of story telling what otherwise could have been a confusing A- Time. You may wonder if the book is so great why did you rate it nine out of ten, and not ten out of ten? The book is great, but there are a few moments where you just say to yourself this part is stupid. I read the advanced copy so the writer might have changed it. These few moments are not enough to ruin the book. This book ends how I think every book should... with suspense. This book is the first in what I think will be a trilogy the second book, Inrage (that I am anxious to read) is already out and the third book BlindSighted will be released Nov 30,2006 according to amazon.com. In closing, I highly recommend Yestermorrow: Time Trippers to teenage readers of science fictions. This book is a must read!