The first I can remember reading is the first part of Fellowship of the Ring; the English teacher had it in a shelf of books we could read whenever we were done with whatever work had been assigned. I started it like four or five times, would usually get to the Council of Elrond and something would come up and I'd forget about it.
Then my Uncle Jake heard about this and bought me a boxed set of the Trilogy + The Hobbit for Christmas that year. I read The Hobbit, liked it, but never got around to that huge trilogy until later.
The other big influence was a trip to the Air and Space Museum in Huntsville. They had a gift shop with all sorts of science-fiction in it, and I picked up Larry Niven's Tales of Known Space. That probably influenced me more than anything else at the time. I picked up a lot of the Gerrold Star Trek episode novelizations.
Then after I discovered D&D, I went back to LotR and read it. After that, I started in on a great deal more. The fiction in The Dragon was a great resource, and I started to read Magazine of Fantasy and Science-Fiction, and Analog. I was much more a Star Trek fan than a fantasy fan in the beginning, so SF initially held a greater appeal to me. Also, SF was more likely to show me something I'd never seen or heard of before. There just wasn't a lot of great fantasy readily available at the time; that wouldn't start happening for several years more.
Then, I met early GM of mine also ran a bookstore and had been a bibliophile for years. He had a living room covered in floor-to-ceiling bookshelves full over everything from fantasy to engineering.
From him, I got a lot of the early fantasists: Dunsany, Lovecraft, Derleth, Wellman, Leiber, etc. And I started haunting the used book store in town when it was still good, and came away with the Adult Fantast series of reprints and new treasures. That made me start reading more and more fantasy.