There are many excellent books written about NVC, by Marshall Rosenberg and other authors. You can buy these books from Puddledancer or Amazon.com. Other books on NVC, can be found from the NVC World website.
Brooke Summers-Perry, one of our local facilitators, is currently writing a series of children's books inspired by NVC.
Video and Audio
There are many useful videos and podcasts available describing the basics of NVC or providing examples and tutorials. For example, the YouTube NVC Academy channel and other interesting videos can be found in this comprehensive YouTube playlist.