pb?Paperback. Typically 7" by 4.25" (18 cm by 11 cm) or smaller, though trimming errors can cause them to sometimes be slightly (less than 1/4 extra inch) taller or wider/deeper.
Notes: Info from Archive.org copy. "7th printing 1979" on copyright page. Other prices on back cover: Australia $2.95, New Zealand $2.95, Rep. of Ireland 93½p; "Not for sale in Canada". Last page is unnumbered.