I've been writing since I was old enough to understand the words and concepts that make up a story. But I didn't start taking writing seriously until I was twelve. I was very into video games at that time, and I played a particular game that inspired my first "real" book. That story has evolved a lot since then, and I hope to one day get it published.
In my personal opinion, relatable and dynamic characters. If I'm unable to relate to a character, especially the main character, then I have a hard time getting invested in the story as a whole. Make me care about the character(s), and I'll more than likely enjoy the book.