I think most of us have our magical gateway drugs - the books or movies that convince us as children that magic is real, and do such a good job that we never quite stop believing it.
For me, one of those books is So You Want to Be a Wizard by Diane Duane. From this book and its sequels I learned that words are power, and that the way you describe something subtly changes that thing. I learned that reenacting stories gives them power. I learned that magic is dangerous and still worth it.
I don't think there's any shame in admitting that fiction influenced the building blocks of my magical practice. Diane Duane and a few other authors had more influence than most of the actual pagan authors I've read. Some people will scoff at that, but our influences are what they are. I'm not going to apologize for that.