I was a compulsive reader as a child, sometimes reading several novels in one day. The one that influenced me most was Mary Wollstonecraft Shelley's Frankenstein, or: The Modern Prometheus, which I read at 14 . It was my first encounter with a deeply introspective novel, so you can imagine my sympathies lay with the creature, not the creator. I was bowled over by the early scenes of Frankenstein's creature observing the woodland family, as this contrasted so much with the Boris Karloff movies then being reshown on British television.
I have since lost my enthusiasm for any form of horror, but Frankenstein remains a firm favourite as a piece of introspective literary fiction.
For more on my influences see my bookshelf on that topic, or my Pinterest board