I've written professional articles on various industries, etc. which were published in relevant (sadly boring) industry magazines.
Also short stories for fun with some small successes in competitions.
Thinking of taking a proper stab at writing a novel but need to allocate time (likely to come out of gaming, but hey you've got to make choices).
I also tend to write very informed but too long entries like this that I strongly suspect few read as they look as daunting as the last four Harry Potter books combined.
Try to be reasonable... its easier than you think...