A page number is required if you are quoting. When paraphrasing, or if the information you are citing can be found on a particular page the APA publications manual 6th edn (p. 171) encourages you to provide page numbers to help the reader locate the information.
(Karskens, 1997, p. 23)
Ward (1966, p. 12) suggests that ...
If you are summarising, or only citing the main idea of the book:
Include information in the following order:
- author’s surname, and initial(s).
- year of publication (between parentheses).
- book title (in italics, capitalise first word of title and subtitle, and proper nouns).
- edition (if other than the first), (between parentheses, after the title, but before the full stop).
- place of publication (city, initials of state, if published in the USA; city, country, if published elsewhere) followed by a colon (:)
Karskens, G. (1997). The Rocks: Life in early Sydney. Melbourne, Australia: Melbourne University Press.
Yaffe, D. (2006). Fascinating rhythm: Reading jazz in American writing. Princeton, N.J.: Princeton University Press.