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

> Oidce sa Coill = The class/lesson/teaching in the woods/forest

> Oidce tar Oidceanta = Lesson upon lesson

I suspect these are actually mistranscribed by the project. That looks more like it should be "Oiḋċe sa Coill" or "Oidhche sa Choill" without the ponc séimhithe, and in modern spelling "Oíche sa Choill" - "A Night in the Forest". Comparing the transcription of the first chapter with the source in the PDF they're missing a fada (an acute accent for non-Irish speakers) in "ná".

Similarly, I'd probably render the second one as "Night upon Nights".

And she's not just any Máiréad Ní Ghráda; this is the same Máiréad Ní Ghráda who wrote An Triail and Progress in Irish!

> An Tróid leis na 'Cráidmí' = The war with the Craidmi

The battle/fight with the Craidmi. troid is singular whereas war is plural.

Not an Irish speaker, but I've seen some of the names and terms while reading folklore. Is it possible that Lug Lám-fada is a proper name/epithet for "Long-armed Lug" (alluding to the god Lug) instead of a descriptor of a "long-armed lug" object?

Maith thú

"An t-Éalod" I think would be "the escape"?