I just had a look for the Robert McKee book out of curiosity, and it looks like it's really hard to buy an ebook but there's a version available for free on archive.org: 'Story' by Robert McKee. (Hopefully a legal one? But I'm surprised.)

You probably want to read the bit on p. 35 where he talks about scenes and beats, and then p. 147 where he talks about 'The Gap'.