Blood Scrivener reads:
If you would draw a card while you have no cards in hand, instead draw two cards and lose 1 life.
If I cast Divination as my last card, how many total cards do I draw?
You draw three cards and lose one life.
"Draw two cards" means "Draw one card. Draw one card."[CR 120.2]
For the first draw, Blood Scrivener's replacement effect would kick in. You draw two cards and lose one life instead.
For the second draw, Blood Scrivener's replacement effect would not kick in because you have two cards in your hand.