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.
This book collects the first six scripts from the third season of Buffy the Vampire Slayer. Reading the scripts allows you to experience the story itself without having your opinion or perception swayed by the appearance of the actors, the sound of the music, the lighting or direction or other production values, or anything other than what was captured by the writer on the page. It's also interesting to spot differences from the original vision from what was finally realized on screen, reading the occasionally amusing stage directions, etc. The scripts range in dating from July to September of 1998, but still read as fresh and vibrant, as I've said of every volume. The first story is Anne, written by Joss Whedon, and shows how Buffy has spent her summer in trying to deal with the season two finale. In the next scripts, we see what her friends and family have been up to, new characters are introduced (Faith and Trick and Wesley, etc.) and we see that life must go on. It's very impressive how one character can be featured in one episode and then turn up again later and be re-introduced in context rather than by summary; Joyce, for example, pops in and out and always seems to fit. It's a very enjoyable read, though of course enhanced by appreciation of the filmed versions. I'm not sure by this far along in the story how well a new reader, unfamiliar with most of the backstory, would be able to parse all of the relationships, but there's always the monster-of-the-week to keep things rolling, and the beginning of a new overall arc.
Let me explain the discrepancy there--really liked it, but couldn't finish it. Well, I pretty much know the series by heart so the only script really worth reading was the first one, by Joss, b/c his stage directions were pretty darn hilarious.