The following books about Waterford History are available to download free of charge. They are all of interest, particularly Charles Smith's book. It should be kept in mind that the books are products of their time. Some of the historical conclusions or facts may have been overtaken by current research. This is particularly true where the authors deal with pre-history. P M Egan's book is quite well known for containing inaccuracies but it is still a part of the canon of Waterford historical literature.
The ancient and present state of the county and city of Waterford (1774) 2nd edition
R H Ryland
The history, topography and antiquities of the county and city of Waterford; with an account of the present state of the peasantry of that part of the south of Ireland (1824)
The History, Topography and Antiquities (natural and Ecclesiastical) with Biographical Sketches. (1870)
The story of Waterford: from the foundation of the city to the middle of the eighteenth century (1914)
P. M. Egan
History, Guide & Directory of County and City of Waterford (1895)
Thanks to Ivan Fitzgerald for sending on these links.