When I got my vehicle registration card, I wondered the same thing about the registration book.
I had a similar experience when I moved states and had to deal with the local DMV. What I found out was that while the card is super handy for day-to-day stuff, like traffic stops, the registration book might still be needed for certain transactions, like selling your car.
It's always good to double-check with your local DMV to be sure about the requirements. They're usually really helpful with this kind of stuff.
