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.
A book with relevant vocabulary for the JLPT N1 and many exercises. The words are in Japanese only, so you have to look them up yourself, which can be a bit tiring, but this way you can use it no matter what your mother tongue is. I enjoyed the Kanji book more, but it's a good book for studying.