It will sound ironic, coming from me, to recommend a very non-scholarly book, but the best hand collection I know is Soodlum's Irish Ballad Book. The notes are abominably bad (don't trust anything it says), and it occasionally sneaks in some very non-Irish songs (e.g. "The Leaving of Liverpool"), but it has lyrics, melodies, and mostly-usable chords for a whole lot of songs. Most of the books recommended here are good for understanding a particular aspect of Irish music, but if I wanted to haul something to a jam session, I would without hesitation choose Soodlum's.