The mind of a wizard is more open to the more esoteric elements of his surroundings Ã¢â?¬â?? this is why he is able to perceive the weave of the Great Tapestry that is the multiverse, and pull at the strings. This increased sensitivity can manifest in several ways.
It looks like a cook's book. It is a cook's book. It is also where the cook, who happened to be a master spy, encoded all his secrets and contacts. The book has innocently fallen into your group's hands. Everyone wants it, and many are not subtle or peaceful in their attempts.