From the introduction:
Imperial Age: Grimoires is designed to add realism to hermetic traditions in Imperial Age Magick campaigns. Unlike the stereotypical fireball-throwing fantasy wizard, hermetic disciples performed elaborate rituals (or incantations) to produce magickal effects. Many of these rituals were interpreted, duplicated, and translated from ancient sources and codified in a book, or grimoire, from which other members of an occult society could study and implement.
This supplement describes the basics of ritual magick, enhancing the material found in Imperial Age: Magick. It also details four grimoires which can be used as-is or modified for your Imperial Age campaign. For your convenience, this supplement also contains a complete Imperial Age spell and incantation list compiled from the Modern SRD to be used in the creation of your own grimoires.