I could tell you I wrote Far From You because I wanted to write a book that took teen love seriously. Or that I wanted to write a book about two girls in love. Or because I've always been fond of puzzles, and juggling timelines and a mystery is the best kind of puzzle.

All these things are true. But the core truth is this: I wrote this book because of 57 words.

Each book idea comes to me differently. Once, it was staring at an oddly-shaped stump near the river, on my daily walk with my dogs. Another time, an image flashed in my head: a girl, walking down a highway in a prom dress, her heels swinging in her hand. A sunset, a want ad, a boy with a face full of secrets, anything can lead a writer down the path of "What if?"

For Far From You, it was three sentences, scribbled in a notebook and the image of a boy and a girl, full of grief, and kissing for all the wrong reasons:

Later, I stare at his face in the moonlight and wonder if he can tell that I kissed him like I already know the shape of his lips. Like I've mapped them in my mind, in another life. Learned them from another person who shared his eyes and nose and mouth, but who is never coming back.

For a month, I stared at these three sentences, and asked myself why and who. Why were these two people – the ones who would become Sophie and Trev – so sad? Why was this moment of grief-fuelled passion a bad idea for them? And who was the girl who haunted them so? That last question was the biggest. And the hardest to answer.

Mina was a character full of secrets. Of fear. Of great cruelty and even greater sweetness. I struggled in her creation. To balance the good and the bad. I tend to write about girls who are on the cusp of becoming. Mina was the first character I created who died before she was able to. Because of this, I couldn't utilize my normal writerly tricks to get to know her, such as writing scenes from her point of view for my own use, to understand her thought process and her motivations better. I needed parts of her to remain secret even to to me, the person who created her, because the mystery of her was so central to Sophie's journey.

But in my mind, I was always writing a love story. One that was wrapped in a murder mystery bow, but a love story at its core. And that was the key to opening the lock that the book lay behind. I've always been fascinated by love as fuel. The fuel behind Sophie's journey, behind all of Sophie's actions, is love. And love is not always healthy or kind or easy. But it can push you onto paths that you would've never journeyed without it. Sophie is pushed by Mina. To be better. To be ruthless. To keep secrets. To hide. To get clean. To find the man responsible for taking Mina away from her.

Love makes Sophie who she is. Love make her strong.

When I came to understand this, in that month where I stared at those three sentences, trying to figure out the girl we meet as she's dying, and the girl who is left behind, I was able to start writing their story, their shared past and Sophie's lonely present.

Love makes the story. Love makes the character. And love fuels the writer.