From inside the walls of women's prisons in Nova Scotia, this is a book that challenges the nature of prisons to keep people isolated and silent. Compiled by Books Beyond Bars, a grassroots activist project in Halifax, this small tome brings together poetry, texts and artwork by women locked up by Canada's prison-industrial complex.
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.