Unfortunately out of print this long while, Irish Traditional Food is perhaps the best of Irish cookery books. Dealing with recipes from 16th century and stopping somewhere 'round the 1950s, this is a no non-sense guide to the real food of Ireland with none of that quare foreign stuff that we started aetin' (but never learned how to cook properly) in the last few decades. You'll find no ciabattas or currys here or 'healty lifestyle' foods, but lots of oats, cream, goose fat and crubeens (pigs feet). And if you like your tripe & offal, you'll be happy as Larry.
Shellfish & spuds and some more humble ingredients like nettles & watercress are all covered in great details, not to mention a very impressive chapter on baking.
Overall, don't mind all the fancy pants who currently hold the spotlight on irish cooking, Fitzgibbon's book was around before them and still hasn't been topped. Very highly recommended.
I'm starvin' now...