[nbanks]

Presuming you still can't borrow a new book if you have overdue books at home, and you still have to pay for lost books, this seems reasonable. It reminds me of the old-school netflix DVD rental system where you can keep a movie as long as you want, but can't get a new one until you return the previous one. It also reminds me of being able to take out books for 3-5 months at a time as a grad student--it was so much nicer than undergrad!