The following titles are considered classics on the murky subject of how to write well.
I encourage you to avail yourself of several of these titles. They are nuts and bolts works, very practical, and you could make some major strides in your writing by reading and studying them. They cover both fiction and non-fiction and are worth their weight in gold.
THE ELEMENTS OF STYLE, Strunk and White (this is #1 for a reason)
THE CRAFT OF WRITING by William Sloan, OP, available on used book market.
THE LIE THAT TELLS A TRUTH: A GUIDE TO WRITING FICTION by John Dufresne
ON WRITING: A MEMOIR OF THE CRAFT by Stephen King
THE EYE OF THE STORY: SELECTED ESSAYS AND REVIEWS by Eudora Welty
ZEN IN THE ART OF WRITING: ESSAYS ON CREATIVITY by Ray Bradbury
THE ART OF FICTION: NOTES ON CRAFT FOR YOUNG WRITERS by John Gardner
ON BECOMING A NOVELIST by John Gardner and Raymond Carver
LIVING BY FICTION by Annie Dillard
BIRD BY BIRD: SOME INSTRUCTIONS ON WRITING AND LIFE by Anne Lamott
INVENTING THE TRUTH: THE ART AND CRAFT OF MEMOIR by William Zinsser
WRITING IN GENERAL AND THE SHORT STORY IN PARTICULAR by Rust Hills
A STAY AGAINST CONFUSION: ESSAYS ON FAITH AND FICTION by Ron Hansen
UNDERSTANDING THE ESSAY by Foster and Porter
THE BEDFORD HANDBOOK (for grammar, punctuation, syntax and usage)