Mass market paperback : Also known as the pocket paperback. A small format paperback usually measuring about 4" by 6".

Ex-library : A former library book, generally containing library acquisition and ownership stamped markings, and other typical indications of the library's use.

remainder mark : Usually an ink marking of some sort which indicates that the book was designated a remainder. In most cases, it can be found on the edges of the text block in the form of a marker stripe or a stamp of some sort.

Remainder marks considerably lower the overall collectibility of a title, although, in some cases, they are acceptable to a collector.