As you know I’m trying to teach myself Irish these days. My main sources are two books: Learning Irish by Micheal O’Siadhail and a three-volume set of Buntús Cainte which is, I think, an interesting and effective combination. I don’t want to fully review either of them but let me just say how their philosophies compliment each other.
“Learning Irish” is very demanding and grammar-heavy. The explanations are succint and you really have to pay attention or you’ll miss a footnote with an essential point. It progresses in a very systematic manner, one which aims at giving the learner a sound understanding of the inner workings of the language and not at getting him to speak as soon as possible. As a result, there are no chatty dialogues and for one-third of the book you know just one verb – to be. If you are patient, by the time you reach the end of the book, you’ll have achieved a solid competence in Irish, be sure of that. There are many exercises (and the key!) and all the reading passages are translated. The variety being taught is Cois Fharraige dialect, a variety of Connamara (ie. western) Irish, which again contrasts “Learning Irish” with “Buntús Cainte” because the latter teaches Standard Irish (but SI is sort of close to Connamara, so that’s not a big problem).
If “Learning Irish” is serious then “Buntús Cainte” is above all fun. It gives no dull explanations, has lots of cute and funny pictures and teaches conversation right from the start. The point is, going by it alone, you would never get the idea that there are two genders in Irish and thus you wouldn’t be able to predict eg. if a new noun is lenited after an or not. If you learn your grammar elsewhere, “Buntús Cainte” serves as an excellent source of conversation patterns.
In short – I recommend them both, but only in tandem.