The Chamberlain Family Book of Shadows is the spell book of the Chamberlain line of Witches, one of the six families that settled in Chance Harbor after fleeing Salem. Its current location remains unknown ; it was probably hidden after the events of the Boatyard Fire.
While a list has yet to be determined and Thomas and Henry Chamberlain hadn't been seen using magic, it can be speculated that some of Dawn's knowledge of witchcraft came from that book since she was the wife of Thomas, a Chamberlain heir.