There was a series by Lloyd Arthur Eshbach written in the 80's and 90's that has some celtic mythology interwoven into it. Beyond the Gate, I think is the first in the series.
You might find the "The Endless Knot" series by Steven Lawhead a time travel story which weaves celtic mythology into the plot very effectivly. I read the triology before I knew much about the myths of the celt and then when I began to learn them I kept remembering Lawhead's novels saying to myself "Hey! that was in the Endless knot books.
They are available through www.audible.com .
Slainte'
Bill & Sir Brinkley the Exubrant my LeaderDog.
May all your blessings be the ones you want and your friends many and true.
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