Mirror in the Sky is a first novel for young adults. Anyone who ever navigated high school from an outsider's position, and anyone who has ever dreamt of alternate universes with alternate Earths should really enjoy this book. I read it in one sitting, without a moment's thought of putting it aside to finish the next day. Without spoiling anything, the protagonist of this story is dreading her upcoming junior year of high school, yet another year as a lonely outsider made even worse because her one friend will be at a year abroad in Argentina ... when something happens that is so incredible that it threatens to completely overshadow the drama of high school social life (and yet doesn't, quite: is anything more profound to a teenager than social life?). A planet is discovered that appears to be a lot like Earth, and as more transmissions are received, the similarities grow from surprising to eerie. Many mysteries are left for the reader to ponder at the end of this book, along with thoughts such as the following: "That's the odd puzzle of time: It's a shoreline that keeps eroding. Every time you look, you're struck by the realization that once upon a time there was more -- the more that you never really saw, because all you ever saw was the past."