The two books I've read so far that made a difference is Save The Cat by Blake Snyder and Writing For Emotional Impact by Karl Iglesias. And for purely editing rules, The Screenwriter's Bible is good.
Blake Snyder's book is focused on structure and plotting -- how to breakup down the flow and elements of a good story, and where in the story each element should occur. Karl Iglesias's book is wonderful at pointing out how to push the viewer's emotional buttons. He claims (and I agree) that people don't go to movies to be entertained, they go to have an emotional experience, and his book goes in depth about how to give them what they want.
But reading books are only part of the story. It takes reading scripts. There are a number of websites that allow people to download scripts of famous movies. A Google search on 'movie scripts' should show dozens. Some charge a small fee and some are free. But scripts are by far the best learning tools. I've read hundreds of them. The great thing about scripts is that they read fast. I can read one in a single day. They are normally 100 to 120 pages long (rule of thumb is one page for every minute of film) and it's mostly dialog, which reads fast.
The other huge thing that has helped me learn is my weekly screenwriter's group. Six screenwriters meet every Tuesday morning for 2 hours. We critique each other's work and help support each other in the difficult task of screenwriting. That has really been invaluable.
Writing scripts is not easily. A writer need to pack a lot of elements into 100 pages without every becoming boring. It takes work, but it's oh so satisfying when it all comes together.