Please note that the author is actually Althea Douglas, not Douglas Althea; I'm not sure why GoodReads has it reversed, but there seems to be no way for users to correct it.
I read this book as the primary text in a genealogy class on using maps in genealogical research. It is a thorough and interesting book that should prove helpful to any serious genealogist/family historian. There are several sections of this book from the Ontario Genealogical Society that are specifically targeted towards those researching in Canada at some point in their research (be it recently or longer ago), covering this subject so thoroughly that the detail may be overwhelming for those not interested in this aspect, but these sections are easily skipped by those not specifically researching in Canada. This book has inspired me to do much more work with maps than I had previously done (and I had already used maps more than it seems many other genealogical researchers do), which to me is a testament itself of the helpfulness of this book.