I have always advocated doing everything possible to pay off credit card balances; it's good financial management and the ticket to a strong FICO credit score. ↗
I love, love, love that you want to use your debit card. But to keep your credit score solid, you still need to keep a few credit cards and use them at least once every few months. ↗
Credit card companies pay college students generously to stand outside dining halls, dorms, and academic buildings and encourage their fellow students to apply for credit cards. ↗
With paper printed books, you have certain freedoms. You can acquire the book anonymously by paying cash, which is the way I always buy books. I never use a credit card. I don't identify to any database when I buy books. Amazon takes away that freedom. ↗