Futhark by Edred Thorsson was an early influential read... as an eclectic ritualist I still use the runes and this was the first book to introduce me to using them magically. At sixteen I was given a copy of The 21 Lessons of Merlyn, while this book hasn't aged well, in terms of its content, for me, it did stir my interest in Druidry which continues to this day. When I found a copy of Crowley's The Book of the Law in a used book store later that year it was at first unfathomable. Thelema became important to me later, though I would hesitate to call myself a Thelemite. Nuit and Hadit remain important in my practice, though other aspects of it, not so much at least right now.
I also remember being in a bookstore when I was in middle school looking at a copy of 777. It was a mystery to me. An older teen said to one of his friends about me, "He'll never understand that book." It made me so mad I made a vow that I would understand it!
Faoladh already mentioned Modern Magick. A friend of mine had an interesting story about that book... when he got sent away to a Baptist boarding school, he ripped the book into different sections and smuggled it in via a binder and folders.
I always love to talk about books... thanks for giving us the opportunity to share these formative moments when I was first exploring my textuality Taylor.