A book in good condition should be a rectangular solid when at rest, whether upright or on its back, with the covers at right angles to the spine. If a book is out of square, usually from resting crooked on a shelf, or leans to the right or left when on its back, it is , or . If the covers bend in or flare out, usually from rapid humidity changes, a book is (bent like a drawn bow). Thick hardbound books also tend to have their pages sag downward in the middle even if they are sitting level on a shelf.
A book in [Good] condition is a book which has seen a little wear and tear, though is not in any way unusable. The book is functionally whole, but the binding side may be worn from use or the pages may be folded over to keep a good bookmark. A book in Good condition will never be in disarray or falling apart, it will have all of its pages and will be very readable. It will be noticeably used though.