Brilliant question worth an entire article in itself, but here's my short 2 cents' worth based on information we currently have.

Content, information and products meant to be publicly available either freely or for cost will require appropriate labelling. Say if a birthday card in the supermarket uses a picture generated by AI, on the back of the postcard it will have to state something like "graphics generated by X tool". Same would go for your book. You'd basically disclose what was AI generated. I think there will be a threshold. For instance, replacing red eyes in a photo with AI would not need to be disclosed.

When it comes to private content, I don't think anyone will care. You making a birthday card for your friend should be totally fine. It would be seen as personal and non-commercial use and also... nobody is going to check.

It will be interesting to see where exactly the line will be drawn, but I imagine it will be somewhere between personal and publicly available content/info, so stuff posted on Facebook for instance would need to be labelled.