2.5B7.

Unpaged Books:

Except for rare books, do not follow the rule. Instead, record the extent statement as:

1 v. (unpaged)

N.B. The Library of Congress applied the LCRI as written, which results in a reduction of data given in the bibliographic record. Other libraries may wish in certain or indeed in all cases to give the fuller data without this reduction. In this respect bibliographic records must be considered equally valid or "correct," no matter which of the two practices is followed. This policy is especially important in the context of LC’s handling records originally created by other libraries when LC is using them in its own cataloging: the fuller data should be left "as is."

See also:

2.5B. Number of volumes and/or pagination