First? It's either The Humans of Ziax II / The Drought on Ziax II, by John Morressy, both stories published together as a tête-bêche; else it's Stranger from the Depths by Gerry Turner. I got them both in the same year ('77 or '78) from the Scholastic Book Fair at my school. Remember those? I make a small hobby of collecting vintage Sci-Fi titles, mostly for the artwork, tbh. If you click the link in my signature, it'll take you to the page I created for them.
I'm pretty sure it was The Incredible Shrinking Man, probably around 1961 or so. I can't remember if it was that book that had a pretty good sex scene or two (I would have been 12), but I remember reading something that summer that did.
My first one was when I was about 12 or so. 20.000 Leagues of Submarine Journey. I switched to Asimov's Fundation that lead me to Martian Chronicles and the snowfall effect was then unstopable. After years in a DeSciFibrilation Center ruled by Klingons, I joined the Rebellion of the Classics in the H.G Wells's frontlines. I was soon tranferered to the Ender's Fragate against the Buggers and I'm still somehow in the Hadelman's endless war against the Taurines (just waiting my three-thousand-years-of-duty paycheck). I've traveled to the Revelation Space and done many things I can't scream. In short, I retired from the active services and now I survive as a writer of fortune... but my real name is Legion.
To look at the question a different way, I think my favorite "first book" could be classified as an author that I discovered by myself. As I mentioned, my dad has an extensive library of F&SF, and a lot of my friends are readers too. One day in the mid-90s though, I was in the local bookstore and saw an interesting title. Not one of the ones being promoted, showing off the cover, but one that was just down towards the bottom, spine out. The title intrigued me, the layering of the book took me a bit to figure out, but once I was in, I was hooked, grabbing everything Mr. Banks had on offer. Got a little confused by the "Iain M. Banks" vs. "Iain Banks" naming convention, especially since the first non-M I read was Complicity, which is quite different from his SF work (and one of my least favorites. There has to be one, no?). But anyway, Iain (M) Banks was the first author I found all on my lonesome, and he had a tremendous effect on me both as a reader and a writer.
Yup, and the book was titled just The Shrinking Man. Matheson wrote a lot of stuff members here would recognize, including the Twilight Zone episode with William Shatner and the novel that the film What Dreams May Come was adapted from.
First book outside of school would be Salem's Lot by Stephen King. First syfi/fantasy would be The Hobbit.
When I was a youngster there was this book... "Where The Wild Things Are", don't know if it is still in print. Book scared the hell out of me at age 7. Does that count as Sci-Fi/Fantasy?
