For those looking for a good source on Celtic mythology, check out James MacKillop's
Dictionary of Celtic Mythology, published by Oxford. It's excellent: both highly detailed and carefully researched, and unlike many such books, tries to cover as many viewpoints as possible without breaking down into confusion. If you want to start with a single book, I couldn't recommend a better one.
There's also Peter Berresford Ellis'
Dictionary of Irish Mythology, also published by Oxford. It is a bit trimmer and the text is somewhat more accessible. (Ellis is a writer of fiction as well, under another name, and his prose is a bit more flavorful, IMO.) It isn't nearly as expansive, however. Ellis also wrote a
Dictionary of Celtic Mythology, but it has some issues due to poor editing after it left his hands. I hate to say it, but I'd recommend avoiding that one.
There are many other good texts, but those two are among my Favorites. They are readily available, inexpensive, unbiased, very knowledgable and well-written.
For those looking for a good bit of authentic Irish myth, you might try Thomas Kinsella's translation of the
Tain bo Cuailnge, which is published simply as
The Tain by (again) Oxford Books. Kinsella is a noted poet and expert on the language. His translation was done as carefully as possible to maintain the original flavor and feel. It also comes with extensive notes detailing his sources, various comments on the text, interpretations, and so forth. It is also an amazing action-adventure tale. One man versus an army led by a beautiful woman. Try and top that, Hollywood!
For those looking for a good snooze instead, you can try the research paper I once wrote on the
Tain. It is a bit longer than the Dom II manual and makes for an excellent sleep-inducer.
