When I was a teenager, I discovered science fiction magazines. Astounding (which became Analog) was my favourite, but "if" was a close second, followed by "f & sf". I was able to buy them second hand at the market for sixpence each, and my collection of these was my first owned library.
I learned a lot from these magazines, and they reinforced my love of maths and physics. I remember at my university interview, one of the questions they asked me was the difference between science and superstition. I'd just read an editorial in Analog about this, and I pretty much regurgitated that for them.
When I went to university, there was a science fiction book club; I joined that and systematically read my way through their shelves.
I've just found out that a complete set of "if" is available online. All 187 of them. I've downloaded all of them in pdf format, and I'm putting them on my iPad now (the Kindle isn't really big enough for pdfs).