My Dad introduced me to SF by lending me his copies of the ER Burroughs books (I inherited these when he died last year).
I then discovered that my local library was full of SF - first the Heinlein and Blish juveniles in the childrens' section and then the Heinlein and Blish novels for adults in the adult section. Of course, there were many other SF writers featured in the adult section: Anderson, Sheckley, Galouye, Sturgeon, Herbert, Aldiss, Ballard, Simak etc., etc., etc. Anyone remember the Gollancz hardcovers with their hideously dull and inappropriate yellow and magenta covers?
Next I discovered that, about 20 miles from my home town (Peterborough, UK), in the small Fenland market town of Wisbech, there was a shop devoted to SF (what joy!). The shop was called 'Fantast (Medway) Ltd.' (I never did find out what the 'Medway' bit represented) and was run by a couple called Ken and Doreen Slater. Their shop was a treasure trove - full of all the latest American SF paperbacks ('Ace', 'Pyramid', 'Lancer' etc., etc.). These all had very striking covers painted by such worthies as Ed Emsh, Jack Gaughan and Gray Morrow - a distinct improvement on the Gollancz covers! I used to save up my meagre pennies and make monthly (or bi-/tri- monthly, depending on how many pennies I had!)pilgrimages to this shop on the bus.
It was in this shop that I discovered such diverse writers as Jack Vance, Roger Zelazny, Samuel Delany, L. Sprague deCamp and Philip K. Dick.
I have been an SF fan ever since those far off days but don't really read as much as I used to (I'm much more selective now).
If it's of any interest to anyone, the contemporary writer who still rings my bell as much as those 'Old Masters' used to do is Walter Jon Williams. Try his extraordinary urban fantasy 'Metropolitan' and its sequel 'City on Fire' and if you like Space Opera who have to read his trilogy that started a couple of years ago with 'The Praxis' - brilliant!