This is the 90th most frequent Afrikaans word.
waarvan
"Waarvan" means "of which" or "about which" in English.
Here, 'waarvan' indicates 'from which', relating to the point of origin of the action (beginning) associated with the idea.
Ek het 'n idee waarvan ons kan begin.
I have an idea from which we can start.
In this case, 'waarvan' stands for 'that we like', connecting the suggestion with the sentiment of liking.
Sy het 'n voorstel waarvan ons hou.
She has a suggestion that we like.
In this sentence, 'waarvan' is used to indicate 'of which' or 'of that', showing the object of fondness being the book.