Off the top of my head, I know that Mark Bence-Jones has an entry for Castle Freke in his 'Burke's Guide to the Country Houses of Ireland', also called 'A Guide to Country Houses- Ireland' or something (published originally by Burke's Peerage in the UK, then republished by, I think, Constable). The book describes the buildings and lists occupants, former and current, and their 'rank' in the peerage- Baronet, Viscount, etc.
Also, Maurice Craig has written about it- I recall a mention in his 'Classic Irish Houses of the Middle Size' (a tremendous book from the mid-1970s that's sadly long out of print, but in most libraries), though the house is hardly 'middle size'- I think he mentions it because of its unusual name.
Start with the Bence-Jones- it's readily available. If you're in the US, your local library could possibly do an inter-library loan with Trinity, UCD, Irish National Library, etc.
Good luck with your search.