I was wondering to what degree celebrity books are ghost written?Some are. It's a dead secret which ones. But it's a better bet, usually, that celebrities' enormous egos have prevented them from accepting "help".
I find it hard to believe that Madonna writes her own children's books.(Rolls eyes) Ahem.
Do publishers actively approach a celebrity asking if they can use their name on a book? Though I would prefer to have my own name on something I've written, I wonder what's involved in getting a celebrity endorsement?If you mean you're imagining a publisher accepting your manuscript and then approaching a celebrity to take credit for it, you can stop dreaming right now.