Two kinds of grandparent book
A book from grandparents to a grandchild, about the things they do together — the Saturday pancakes, the garden, the song only Grandpa knows the words to.
A book for a grandparent, from the grandchildren, about them. These tend to be the ones that make adults cry at the table, because a grandparent is rarely the subject of anything any more.
And when a grandparent is no longer here, a book can introduce them to a grandchild who never got to meet them, through the things your family remembers: remembering a loved one.
What makes it feel like them
The name the children really use. Not "Grandmother" if she is Mimi. The thing they always say, the chair they always sit in, what is in their pockets. A book that gets those right reads as theirs; a book that gets them wrong reads as a template.
When they live far away
A book can be a bridge. Order an extra copy of the same book, and a grandparent on a video call can read the page the child is holding. Extra copies of a Penwynn book cost less than the first.
If the grandparents think in another language, the whole book can be written in it — English, Simplified or Traditional Chinese, Spanish, French, Hindi or Arabic — so they are reading aloud in their own words rather than someone else's.

