Yes, the cosmos map is wonderful but doesn't really cover it, even with an explanatory caption. I guess it depends on what the target audience for the book is supposed to be. If it's intended to be the introductory point to Glorantha as a game setting then the omission of an overview map seems a bit odd. If I bought a book about a setting I didn't know I would be puzzled if the places discussed in the geography chapter weren't shown on a map within the book.