The publication is part of works on England, Scotland and Wales, which together form Topographical Dictionaries of the three aforementioned countries and Ireland.
Local Historians would find this source very useful as it provides a description of the geography and topography of an area as well as details on schools and churches. Many church buildings ffor example, have been renovated or totally relocated (or are now in ruins) and so this information is of great importance for a parish as it fixes a place in time. Following from Lewis, the researcher can can find out more by delving into historical manuscripts, archives of the Education Commissioners, Diocesan archives etc. The Dictionary gives a unique picture of Ireland before the Famine.
It was published with an accompanying atlas, and at the time marked a new and significantly higher standard in such accounts of Ireland.
The entire dictionary is transcribed and can be accessed for free online at Library Ireland