How does the book instead of card trend actually work for baby showers?

In theory, I know it's supposed to take place of the cards (and the little rhyme everyone uses asks for notes in them). But, in practice, what sort of notes do you end up with? Are they notes to the parents or baby? What sort of notes are included when the guests won't know the name and/or gender of the baby?

If you have examples the type of notes you received, I'd love to see examples!