Speculative fiction is the genre that includes both science fiction and fantasy. I think Robert Heinlein originally came up with the term and I find it rather palatable, since both concern potentialities. There's not much difference between fantasy, such as Lord of the Rings, and science fiction, such as Blade Runner. Both are not real, but could happen via sufficiently advanced technology, thus, they are speculative.
For example, all of the creatures seen in the Lord of the Rings movies could be made real through biological engineering. In that sense, all fantasy falls under science fiction. This is because the right technology could make anything a reality.
I have been a reader of speculative fiction since age 14. My first introduction to the genre occurred at age 5, when my mom read aloud A Wrinkle in Time, in the hallway at my old house on Howdershell. I clearly remember being shocked and inundated with a sense of otherworldliness, as if there is more than just what I experience, much more. I didn't start reading speculative fiction on my own until age 14, when I was given the Chronicles of Prydain books, written by Lloyd Alexander. I shortly thereafter read The Hobbit and The Shining. By my early twenties I had discovered Robert Heinlein, Clifford Simak and Isaac Asimov. The bulk of my reading in my teenage years was spent with Stephen King novels, such as It and The Stand, which do almost require years to ingest.
One might wonder why there was a large gap in my reading; why did it take me until age 14 to finally start on my own? I think video games are partly to blame. I got a video game system, the NES, when I was 11. It magnificently occupied my free time, which, at age 11, was abundant. My mom became frustrated at my lack of reading and even paid me to read at one point. It didn't help. I just didn't care. But now, I don't touch video games and have stacks of books that I want to read.
Reading science fiction has proven to be immensely educational, since it has prompted me to investigate real science. I have read many books about particle physics and relativity, which is mentioned often in science fiction. Relativity is something that should be taught to grade school children, because of how simple it is. It just seems particularly daunting.
By now, at age 33, I estimate I've read around 350 speculative fiction books. Less than 20 can be categoried as fantasy, so my primary concern is that type of speculation which is reminiscent of science, although do bear in mind that sufficiently advanced technology could turn any fantasy into reality.
For a long time my favorite science fiction writer was Robert Heinlein. My cousin Ben mentioned some guy named 'Philip K. Dick' and I eventually read one of his novels, titled Ubik. As a result, I read more of his work and he became my favorite writer. My mom used to talk about some place called 'Riverworld', which was written by Philip Jose Farmer (who admittedly had paruresis, like myself) and I checked out one of his books, titled Time's Last Gift. I read more of Farmer and he became my favorite author.
These days I don't have a favorite writer. It's too impossible because there are so many good writers. However, I do have favorite writers. Lots of them. More than 30.
If I had to recommend a starting point for someone in speculative fiction, I would recommend what hooked me. A Wrinkle in Time and The Prydain Chronicles.