It's worth paying for the e-book as he goes into some interesting points, but in a nutshell the core concept is going through your imported photos in three passes: first, quickly pick all the ones that might have some potential merit (e.g. they are in focus and of something somewhat interesting), then go back through the picked ones and quickly rate them from 1-3 stars (1 being "has documentary value", 3 being "potentially a great photo), then take the 3 star ones and spend a bit of time retouching them if needed and giving them 4 or 5 stars if they are really special.
The end result is that you can quickly get down to keeping maybe one in ten photos from a shoot - it makes the whole process feel a lot more manageable and opening Lightroom less scary! Plus, it reduces the amount of photos we store so you need to worry less about the capacity of your cloud solution ;)