Native Irish Speaker and Sci-Fi fan here. What an unexpected delight. For those who might not pick it up , the author name "Máiréad Ní Ghráda" is that of an unmarried (that's the "Ní") woman ("Máiréad" which is like a variation of Mary).

Here's my Translations of the Chapter titles. I'm pretty sure many of these have old-Irish style séimhiú (a dot above a consonant denotes what would now be a h after the consonant) in the originals that have not been translated by the OCR, so there are several missing h letters. If I weren't on a plane over Afghanistan, I'd download the PDF to check. Will update the repo when I can!

   Pláinéid na feaca Súil Duine riamh = A planet no person's eyes have ever seen
   An Radarc, tríd an gCiandracán = the view throughout the [Ciandracan] (this is a compound proper noun, "Cian" is "head" or "brain" and "racán" could be visor or rocket)
   An Turas go Manannán = the Trip to Manannán
   Manannán = Manannán (it's a noun, which is very similar to the Irish term for the Manx and the Isle of Mann). 
   Muintear Manannáin = the people of Manannán
   na 'Cráidmí' = the Craidmi (I think it's just a plural noun)
   An tÁrd-Máigistir = the high Magistrate, or possibly the supreme magistry
   An Priorún = the Priory
   Oidce sa Coill = The class/lesson/teaching in the woods/forest
   An tinneall = the fire
   Oidce tar Oidceanta = Lesson upon lesson
   Lug Lám-fada = the long-armed lug
   An Tróid leis na 'Cráidmí' = The war with the Craidmi
   Diogaltas = Revenge
   An téalod = not sure about this one