A Book of Mirrors, (BoM) is just another (optional) book that Wiccans/Pagans use to record things. While a Book of Shadows details the spells and how to duplicate them (like a recipie book almost), a Book of Mirrors is used to write out your thoughts and feelings about your reactions to the spells and if it acheived what you were doing, or anything that is important to you that concerns magic (personal journal).
As Patty wrote down the spell in her Book of Shadows, she made a mental note to write in her Book of Mirrors how the spell didn't quite work the way she wanted, but had better results.
by Lyndzey920 December 11, 2007