Like New: an apparently unread copy in perfect condition. Dust cover is intact with no nicks or tears. Spine has no signs of creasing. Pages are clean and not marred by notes or folds of any kind. Books may contain a remainder mark on an outside edge.
Very Good: a copy that has been read, but is in excellent condition. Pages are intact and not marred by notes or highlighting. The spine remains undamaged.
Good: a copy that has been read but remains in clean condition. All pages are intact and the cover is intact (including the dust cover, if applicable). The spine may show signs of wear. Pages can include limited notes and highlighting, and the copy can include "From the library of" labels.
Acceptable: a readable copy. All pages and the cover are intact (the dust cover may be missing). Pages can include considerable notes - in pen or highlighter - but notes do not obscure the text.