I think it is an excellent book and quite comprehensive as far as the number of entries is concerned. Entries are generally relatively brief, however. His "Irish Families" and "More Irish Families" have more extensive entries but, as far as I recall, the number of individual surnames included is smaller than in "The Surnames of Ireland". The "Families" books are no longer in print, I believe, so you would have to look for second hand copies. For what it's worth, I would recommend purchasing "Surnames". The only other such book I am aware of is "Sloinnte Gaedheal is Gall" by Rev. Patrick Woulfe. It was published in 1923 but I think it is available on DVD from Eneclann.