I have to admit that I know little to nothing about Brian Boru, and what I do know is what I learned from your article, Flidais.

I recently bought The Lion of Ireland by Morgan Llywelyn, but I have yet to start reading it. While I know that it isn't appropriate to learn history from historical fiction, I feel that Llywelyn is somewhat of an exception. Her books are so well researched and beautifully written that one can't help but to learn from them.

My question is, and without sounding to dumb, is there a good historical source that documents the life of Brian Boru? And how credible is it?

I know that this time period was very limited in historical documentation and even something as well-known as The Battle of Hastings has parts that are disputed among historians.