This method should look like the following:

```ruby
def overdue?
  Time.now > @due_date
end
```

We use the `?` at the end of the method name to signify that it's going to return a boolean (true/false) value. We use the `@` at the beginning of `@due_date` because it's an instance variable - the particular due date for this instance of the `Book` class. We then compare the values, checking to see if the current time is past the due date of the book.