Acceptable: This book has been well-loved by somebody else. It will show wear, have markings in the text, and, perhaps a bit of moisture damage to the pages.
Very Good: This book has also been used before, but a bit more delicately. It might also have writing on the pages, but it will be very limited. It will show minor wear, but will be sturdy and strong.
New: If this book isn't new, you'd never know it. Never read before and hardly ever opened. Clean, crisp and beautiful for reading and display.