I often recommend books about fiction writing to my clients and readers. Very briefly, the three fiction writing books I recommend most are:
1) The Art of Fiction by Ayn Rand. Rand’s book is the best because it so well shows you HOW TO create a story from the writer’s point of view. I believe that her chapter on Plot-Theme (central conflict) is the single most helpful piece of advice about writing fiction.
2) Screenplay by Syd Field. Covers many of the key basics of screenplay writing: Form, plot points, sequences, turning points, and scenes.
3) Making a Good Script Great by Linda Seger. Helpful discussions about screenplay structure, motivation, character spine, and conflict.
Also consider reading The Art of Dramatic Writing (esp. the chapter on Premise) by Lajos Egri and Save the Cat (esp. about loglines) by Blake Snyder.
I am a script consultant/developer.