Fill one, empty one.
Yes, it is possible to carry five pine bookcases by oneself. No, not all at the same time. Yes, they will fit together in the new study. No, that tall one won't fit in the backseat and allow the car door to close. Yes, it's acceptable to close the door as far as you can and then hold it shut with a bungee cord, just for the two-minute drive to the apartment. Yes, you will feel better when the books you hope to keep within reach are in fact on their shelves. Which are waiting for them, and for you. In the new study.