well, let's see...
Chapter Two: Generating Manors has a fairly detailed system for determining the size and income derived from a manorial holding. possibility of a mine on the property and the amount of money (in gp) that would bring in. random tables to determine any special maintenance that may be required during a year. talk about harvests and income (again, listed in gp).
Chapter Four: Generating Towns and Cities. a rather detailed system for generating communities of various sizes. the incidence of various building types and the chances of them being found in different neighborhoods of a city. a system of "influence points" for nobles, guilds, churches, and other major players in a community to get a better grasp of the town's social dynamics.
(some of these tables get very detailed. the random townsfolk "professions" table is a d10,000 roll.

)
on to Chapter Five: Economic Simulator with rules and tables for merchants. buying and selling expensive items and what effect that has on the economy. buying and selling in bulk to make a profit.
Chapter Eight: Generating Kingdoms and Aristocracy. using the area and population of a land to determine the number and sizes of communities, manors, major landholders, etc. how to set up a believable feudal power structure.
Appendix 2: Generating Magical Resources. how many / what types of magic items can a lord expect to receive from his vassals as tribute? (if not in tribute, what would they buy with the coin they do receive?)
Appendix 3: Magical Medieval King Template. for those who believe in the "divine right of kings." kings receive magical powers because they are chosen by the gods to rule their lands.
Appendix 4: Building System. how to take D&D magic into account when building structures. seems to compare favorably to the Stronghold Builder's Guidebook.
i'll be honest -- given your extensive knowledge of the medieval period, about 1/2 to 2/3 of this book is going to be a rehash for you. however, to a gamer who
doesn't have that kind of background, this book is very useful. he doesn't need to read and collate information from seven or eight different medieval history texts; he just needs to read this one book. and it's got gaming stats right next to the historical notes.