How to handle book citations by multiple authors in APA format?

In APA format, when citing a book by multiple authors, list all authors' last names and initials in the reference list entry and for the first in-text citation. Subsequent in-text citations abbreviate using "et al." after the first author's surname. Always list every author in the reference list entry, in the order they appear on the source, using commas between names and an ampersand (&) before the last author. For in-text citations with two authors, use "&" between names each time. For three or more authors, include all names in the first citation; subsequent citations use only the first author followed by "et al." (meaning "and others"). Include the publication year. For 20 or more authors, list the first 19, followed by an ellipsis (...) and the last author's name in the reference list. This standardized method accurately credits all contributors while maintaining readability. It allows readers to locate the full source in the reference list and fulfills essential academic integrity requirements for sourcing collaborative works. Apply this consistently in literature reviews and research papers.