Shelley, I've been thinking about this for a while. First, I think that the National Braille Press has some books on this topic, though I can't remember off the top of my head what they are.
Second, you might want to do a web search on something like "improve writing" and see what turns up.
And then, you might want to ask your reference librarian or contact a community college or university that has a good English/creative writing professor and ask for some suggestions.
Then once you have those suggestions, we can begin to search out the actual books. I know that BookShare has some in the collection, but am not sure how you'd go about finding them. I seem to remember that not too long ago there were a bunch of books in the download list about writing...business correspondence, reports, essays, etc. Maybe if you just put the word "writing" or "write" in the BookShare search engine, you will get some hits.
And finally, if you want to improve on a particular kind of writing, then you can read authors who are particularly good at it and take note of what they do. For instance, I've been interested in improving my ability to write an essay, since brevity is not one of my strong points, <smile>, and so I've been reading essayist and paying attention to how they do it. And of course, the very final thing is to just do it. It's like any other skill...it gets better with practice.
Good luck, and share with us what you find of interest.
Peace and Hope,
Gently they go, the beautiful, the tender, the kind; Quietly they go, the intelligent, the witty, the brave. I know. But I do not approve. And I am not resigned.
-- 'Dirge Without Music', Edna St. Vincent Millay