This book has two sections, the first covering the divinatory aspects of geomancy, which includes a brief history, an overview of the geomantic figures, the method of casting a chart, and then several methods of reading it. What is noteworthy about this section is that it contains many elements of teaching that are absent from the original GD documents on the subject, particularly in terms of interpreting the figures that have been obtained. The shield chart is also an extremely useful method of obtaining the figures which works in a very common-sense way. The multiple examples given bring the theory a little closer to home, and there is also some space given to specific questions (and slightly different methods for obtaining the answers for them) such as how to find a missing person or predicting the weather (still as valid today as they were in the Middle Ages).
The second section of the book deals with the magical application of geomancy, and this becomes a lot more obviously GD. The planetary spirits (or genii) and their sigils are covered, along with basic GD ritual like the LBRP. A consecration ceremony for a geomantic box is also given, and skrying and talismans are covered to some degree. There is not much new here for a GD student, however, as it has been predominantly covered before, but it may be of use to those with little or no exposure to GD ritual.
This is an invaluable text for making the archaic instructions of the GD on geomancy make a lot more sense. It provides additional instruction for those who have already mastered the basics, but are struggling to interpret a full geomantic chart. I think it's time that this system gained more exposure in the magical community and that more people practice it, and Greer's book will aid greatly to that end.