A lot of this won’t apply to you — much of it is taken up with criticisms of copyeditors — but that doesn’t mean it isn’t thoroughly enjoyable to read Thomas Sowell, one of my favorite writers, on writing.
The best way to improve as a writer is to read the work of good writers, just as the best way to improve at chess, in addition to doing lots of tactics puzzles, is to play through the games of the masters. Murray Rothbard recommended H.L. Mencken as a good choice.
Also relevant to all this is my cautionary piece “Nobody Sells ‘Millions of Copies.’” Nonfiction books sell far, far fewer copies than the general public assumes.