Elsewhere is a four-book collaboration between Cargo Publishing, McSweeney’s, and the Edinburgh International Book Festival featuring brand new work from 50 of the world’s leading authors. The Book Festival commissioned 50 authors to write short stories, poems, or essays, all on the theme of "Elsewhere." Leading writers, including Michel Faber, Alasdair Gray, Ali Smith, A L Kennedy, Alan Warner, Roddy Doyle, and Amy Bloom, together with authors best known for their writing for children and young adults—such as Michael Morpurgo, Andy Stanton, David Almond, and Margo Lanagan—produced work that comprise the four themed anthologies collected in this slipcased boxed set: Somewhere, Here, There, and Everywhere.
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 50).
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.