To add to what Mick has given you, you might want to check out the Celtic Digital Initiative Archive, where much of the out-of-print material is to be found, which has been digitised by various other initiatives (e.g. by archive.org):
http://sulis.ucc.ie/cdi/textarchive-search.phpLikewise, you will also find Irish Sagas Online quite useful; especially Aislinge Oenguso, and the Tochmarc Étaíne:
http://iso.ucc.ie/Irish-sagas-list.htmlI would also recommend:
Gantz, J.,
Early Irish Myths and Sagas (Penguin Books, 1981): Not entirely faithful translations, as it is a book aimed at the wider public.
Koch and Carey,
Celtic Heroic Age (Celtic Studies Publications, get the latest edition). (especially the wooing of Étaín)
Mac Cana, P.,
Celtic Mythology (Hamlyn, 1969) (Brilliant overview/ introduction to the Celtic gods and their analogous Túatha Dé Donann counterparts).
Since you are especially interested in the Túatha Dé Donann, I would highly recommend reading Cath Maige Tuired on CELT and comparing the description of Lugh with Caesar's description of the God he called the Gaulish Mercury from Celt. Heroic Age.
Cian
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Is Fearr súil romhainn ná ḋá ṡúil inár ndiaiḋ
(Amhlaoibh Ó Súilleabháin)
Please wait for corrections/ more input from other forum members before acting on advice
I'm familiar with Munster Irish/ Gaolainn na Mumhan (GM) and the Official Standard/an Caighdeán Oifigiúil (CO)