I mean, really, why would it be encrypted?

[davidjackson]

Personal safety is a good motivator

Yes, but the proof is in the pudding - you make enemies by having more clients, not because you have a bunch of personal recipes.

As bi3mw says, you might encrypt the secret recipe bit, but not the whole book.

But anyway, I think we can discard the notion that this is any sort of medieval workable cipher.