It is an absolute MUST HAVE if you're doing UK genealogical research! It provides maps to the parish boundaries for each of the counties of England,Wales and now Scotland. Each county map showing parish boundaries for England and Wales is placed next to a historical map for that same county. This provides an excellent opportunity to locate parishes in a historical context.
The real gem of this book is the information on the location of parish records. For each parish, the extant dates of the records available for that parish are given as well as the location of where those records may be consulted.
An outstanding reference work for UK genealogy.