The MLA International Bibliography is a very good place to begin your search:
Other online databases include Project Muse and JSTOR.
More sources are listed on the Irish Language and Literature Resource List.
Use the library catalogue to find books on writers. This small selection may be helpful:
Titley, Alan (ed). Scríbhneoirí Faoi Chaibidil.
Essays on the following writers: Máirtín Ó Cadhain, Cathal Ó Searcaigh, Pádraig Mac Piarais, Seán Ó Tuama, Mícheál Ó conghaile, Máiréad Ní Ghráda, Máirtín Ó Direáin, Peadar Ó Doirnín, Seán Ó Ríordáin, Myles na gCopaleen. In addition, there are two essays on literary traditions: 'An Aisling' by Breandán Ó Buachalla, and 'An Fhiannaíocht' by Ruairí Ó hUiginn and Dáithí Ó hÓgáin.
Poetry
Mac Réamoinn, Seán. The Pleasures of Gaelic Poetry. 1982. PB 1331 .P55 1982
Ní Fhrighil, Ríona (ed.) Filíocht Chomhaimseartha na Gaeilge. 2010. PB 1307 .F55 2010
Essays on the following modern poets: Máire Mhac an tSaoi, Michael Hartnett, Michael Davitt, Liam Ó Muirthile, Gabriel Rosenstock, Cathal Ó Searcaigh, Nuala Ní Dhomhnaill, Biddy Jenkinson, Gréagóir Ó Dúill, Seán Ó Curraoin, Micheál Ó Cuaig, Colm Breathnach, Louis de Paor, Gearóid Mac Lochlainn.
Ó Dúshláine, Tadhg & Ní Chléirchín, Caitríona. Filí Innti go hIontach [Léachtaí Cholm Cille XLI] 2011. PB 1201 .L436 v.41
Fiction
Titley, Alan. An tÚrscéal Gaeilge. 1991. PB 1336 .T475 1991
A study of the novel in Irish.
