dagny wrote:Dirk,
IMO the best way to improve your writing is to write.

I agree--practice makes perfect. But for the folks like me, who had things to say but didn't know how to say them, I offer these:
A Writer's Guide to Characterization and 45 Master Characters, both by Victoria Lynn Schmidt
20 Master Plots by Ronald B Tobias.
These are like coloring books for beginning writers. From these, I was inspired to research historical backgrounds, languages, cultures, even did horoscopes for my characters. Of course, the books didn't tell me to do this, they just stimulated my thinking. Then I wrote. JP
P.S. I still research EVERYTHING, because I don't want to be the writer who turns readers off by making a stupid, avoidable mistake. I just have to ask my cop friends what they think of crime shows to be aware of this responsibility to readers.
P.P.S. Don't go for any of those books that promise you can write a book in a day, a week, a month, etc. Those are marketing gimmicks. Some of us work slow, some work fast. At all speeds, you should at least do your readers the courtesy of cleaning up grammar, punctuation, and spelling. You just have to go at your own speed.