The first Professor of History at the University of Wales Bangor was Sir John Edward Lloyd. He is widely recognized for his scholarship in medieval Welsh history. First published in 1911, his two volume text titled "A History of Wales: From the Earliest Time to the Edwardian Conquest" has become the standard for those interested in exploring their Welsh history. Volume II of this text has been reprinted by Barnes & Noble, 2004 and covers the period from the Norman Invasion to the Edwardian Conquest. The book cover of this reprint is shown below.
For me, the value of this work is the documentation that is given in the footnotes. Professor Lloyd is very detailed and his scholarship is demonstrated. It is somewhat difficult to read as a general text due to the Welsh terms and spellings that are so distinctive to the language. However, it gives a clear documentation to the early Welsh resources available to the genealogist. It is a foundation to the reader as both a "reading" and "reference". Please, don't leave Welsh genealogy with out it.