"Since You've Been Gone" by Morgan Matson

Since You've Been Gone by Moran Matson is told by Emily, a young teen girl, who has a best friend named Sloane.  One day she received a letter that has a list of things for her to do from Sloane.  But Sloane is nowhere to be found!  What is on the list?  Does she complete it?  And where oh where is Sloane?  I really enjoyed this book a lot.  The writing is very good and I always looked forward to picking it up again.  It has a really, really good ending too!
(Gerard's review, 5++ stars)  

Have you read this one? What did you think of it? If you reviewed this too, feel free to share your link to your review in the comments. Happy Reading!