What an interesting discussion. We have a routing farm inspection pending (we are a small smallholding with a couple of pigs and about 70 chickens, and are panicking. To what extent will we need to adhere to these rules? I can't seem to pin down how far to take these issues.
For example, issues of storing eggs, we clean ours before we sell them (using a proper egg wash) should we be doing this in a designated place? Will this be checked? And what is a flock book??
Don't panic too much, the inspections are much more about education than enforcement, the inspectors want you to do things right, and should take the approach of helping you to do that. They seem to be most interested in storage of feed, medicines etc.
As for the chooks, the flock should be registered because of its size, but unless you're grading your eggs you shouldn't need to do much more than sell them in clean boxes and give your customers an indication of when they should use the eggs by.
"Flock book" has a specific meaning for some breeds and species (for example most breeds of sheep maintain a central flock book, which holds the details of registered stock) but for poultry I don't know the term.
We (when I say 'we' I mean Rosemary!) maintain (loosely) a record of what hens are in our flocks, when they were bought, their breed etc, but I don't know if that's a flock book. Where did you see the term?