When it comes to casting spells, there can sometimes be confusion as to whether or not it is the appropriate course of action. Of course, there is a spell for everything, from quitting smoking, to landing that great job that you really want--but when is it appropriate to incorporate magic into your life and when is it simply overkill? To be honest, it takes a practiced hand to figure out that magic is not always the best course of action for an everyday problem, but an important part of being a witch is knowing when it is and when it isn't appropriate to cast a spell for something that may or may not deeply affect your life.
A Book of Shadows (BOS), or a Grimoire is a way for a a witch to keep track of their craft. More than that, it is essentially a journal of everything that a witch has learned, thinks is important, and spells that they have cast or intend to cast. It can contain affirmations of the way they live their life, details on the pantheon of deities that they call upon, uses for herbs and crystals, as well as pertinent information about various divination techniques. Suffice it to say, every witch will have different information available to them in their personal BOS. It is for this reason, that it is silly to think that another witch's BOS or grimoire will necessarily be relevant to your practice.