Grasp The Ultimate Mystery Collection: Greatest Hits Series Documented By Various Depicted In Electronic Format

Various is the correct author for any book with multiple unknown authors, and is acceptable for books with multiple known authors, especially if not all are known or the list is very long over.
If an editor is known, however, Various is not necessary, List the name of the editor as the primary author with role editor, Contributing authors names follow it, Note: WorldCat is an excellent resource for finding author information and contents of anthologies, Various is the correct author for any book with multiple unknown authors, and is acceptable for books with multiple known authors, especially if not all are known or the list is very long over.
If an editor is known, however, Various is not necessary, List the name of the editor as the primary author with role "editor", Contributing authors' names follow it, Note: WorldCat is an excellent resource for finding author information and contents of anthologies, sitelink.