McKee is good to start with, but you could also try any of Linda Seger's books (Making a Good Script Great, Creating Unforgetable Characters), How to Write a Hot Script, by Elliot Grove or my personal favourite Alternative screenwriting: Writing Beyond the Rules by Ken Dancyger and Jeff Rush.
Those books won't give too much help on formatting, but you can download a free template from www.digiscript.com, and there's also some advice on formatting here:
http://www.robinkelly.btinternet.co.uk/formatfilm.htm
Hope that helps!
L