Unlike the worlds in which AD&D is set, be they Greyhawk, Dragonlance or soon enough The Forgotten Realms, the world in which BECMI D&D was set was never really fleshed out in any systematic way. In fact it was usually known as “The Known World” without having a name settled for it up until 1991 when the name Mystara will first appear in print. 

This and the upcoming Gazetteers will do much to flesh out the world in which BECMI is set by giving in-depth information about all kinds of areas of the world. In this volume of around 65 pages, we get everything we need to know about Karameikos, a place in which several published adventures have been set and which can serve as a good starting point for new players. We get  details on geography, history, politics, economy as well as notable characters in the Grand Duchy.

All this would have been invaluable information for DMs who wanted a world which felt lived in and in which every detail was thought out. This is the kind of treatment that BECMI players deserved, good world-building supplements, instead of having to divine everything from tidbits of information spread around a number of different modules and sets.