As has sort of been indicated by some of the answers, WHAT you write has a lot to do with the aspects involved.
A strong, well-aspected Mercury in an "articulate" sign or house is a first step to any sort of *lucid* writing, be that fiction or non-fiction, popular or academic.
In RL, I happen to have a number of writer friends and I've published myself, both in academia and fiction. From my observation of the charts I have for published friends, I've found these things to be common themes (if not absolutes):
--Writing SF/F ... strong Neptune and Uranus placements aspecting Mercury. They don't have to be flowing, but they need to be there. The ability to imagine seems to be key. It's not just houses, btw. Every single published SF/F author who let me cast her/his chart had a Mercury in aspect to either Neptune or Uranus *or both*. Other planets might be involved, but it was always one or the other of those two. (That's not to say one can't publish in SF/F without it, but I was struck by the almost overwhelming presence of them .)
--Writing penetrating academic stuff ... Pluto, 9th house, 3rd house, Sagittarius, Aquarius relating to Mercury. Also sometimes Mars-Saturn positive aspects to Mercury. Mars-Mercury alone doesn't necessarily make one careful (as academia requires), just pugnacious. ;> Too much Jupiter with Mercury can cause expansive, but unrealistic conclusions. A strong Saturn and/or Pluto and/or Virgo, and/or Aquarius is good for academia.
--Writing Romance, again a lot of Neptune and/or Venus involved, 5th house, 7th house. (But I'll admit, I only looked at a couple of Romance writers charts as opposed to a LOT of SF/F authors charts.)
Mercury making sextiles or trines to "creative" planets like Neptune or Venus were things I saw a lot of, regardless.
(For the record, myself, I have a Mercury-Pluto-Uranus conjunction in Virgo 7th sextiling Neptune in Scorpio 9th.)