In response to the 'Road Trip Wednesday' topic of the week posted by ya highway, my answer is Flipped by Wendelin Van Draanen.
I've always been an avid reader as a child, but Flipped was the book that made me fall in love with reading and the young adult genre. It's a stand-alone teen romance in a he-said she-said style with two protagonists sharing their view points on shared events. What hooked me was the characterization and the themes of the book. I cried with Juli when she lost her tree, I rooted for Bryce when he tried to make amends, and when I finished the book, I started to see things as well as people differently.
To me, the change in one's self after reading a great book is magic that can only be found in words within pages. It sparked the writer in me, making me want to create that magic for a young child/adult like myself.
I can still remember myself at twelve years old, reading this book in my bed, with tears on my face (it's not a sad book in the slightest, but it struck something in twelve-year-old me), and everytime I reread it, I can feel myself being transported into my younger self.
If you haven't already, check it out. Then watch the movie, because it's just the cutest thing.