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I'm seeking Druidism, Celtic/ Irish, witchcraft E books. Much appreciated to any posted. Recommendations are welcome as well. I have quite a bit of Irish ancestory and decided it makes sense to venerate and work with these gods before the gods of other pantheons first and foremost.

The secret teachings of all ages by Manly P Hall has a reasonably lengthy chapter relating to Druidism, their rituals and beliefs. It's also a great book for background theory relating to all sorts of traditions and i'd highly recommend it. Here is a PDF you can download.
http://www.istitutocintamani.org/libri/ ... l_ages.pdf

I've also heard great things about "Exploring Celtic Druidism" by Sirona Knight, unfortunately i don't have a PDF i can provide you with though. You may have to buy a copy.
Good luck.

http://www.druidry.org/library

There are book recomendations, reviews, essays and articles here that may be very useful to you.

http://emmarestallorr.org/bibliography.html

https://www.adf.org/articles/index.html

If you're interesting in looking at similar traditions, the Natural Philosophers (Plato, Aristotle, etc) are a good place to look as well.

There are also the alchemical philosophers who write quite a bit about the theory of Natural Principles.

Also this: A Druid's Handbook to the Spiritual Power of Plants