I read most of my SF when I was entering my teens. I wasn't interested in the usual teenage Point Horrors, romances and more normal young adult books, 'classics' didn't really engage me, the books we read in school were too easy and the library wasn't especially good. SF seemed to plug that gap by offering something that was aimed at adults but not hugely difficult. And it was about exciting things like telepathic six-legged dogs, spaceships and imaginary worlds rather than stuff like dating. Come to think of it, I probably read fantasy for much the same reasons.

I don't think I ever got completely obsessed as in able to reel off dozens of authors, but it seemed to be a bridge between childhood and adult reading.