James Richards & John Marland 
Basics Film-Making 02: Screenwriting [PDF ebook] 

Basics Film-Making: Screenwriting is the second in the Basics Film-Making series and is aimed both at students on film production courses, as well as those wishing to write a short film. The book teaches the key elements of screenwriting through examining areas such as dialogue, sound, setting, shots and structure. It also provides advice to new film-makers on how to market their productions. This is an essential guide to screenwriting and will teach you to write and produce artistically satisfying shorts.