totally agree with levi
Dubliners is his masterpiece. was my favourite book for years and even though it is almost 100 years old it's one of the most accurate portrayals of ireland even today.
many sublime parts: the haunting "Counterparts" an "A painful case" and the magnificent ending to "The Dead" one of the best paragraph's of writing in the english language.
Portrait of an artist is a great accesible piece of thinly diguised autobiography. (check out the work in progress version called Stephen Hero)
Ulysees is a difficult but rewarding labyrinth that has some fantastic scenes particularly the one in which the Cyclops appears.
Finnegan's Wake is an intelligent experimental dead end and sadly marks the point where he started writing riddles for critics rather than books and also where his mind tipped over the precipice from genius to lunatic. did succeed in desecrating the englsh language which is probably the most admirable thing a drunken irish man can do.
all worth checking out but i'd advise an annotated version of Ulysees and probably give Finnegan's Wake a miss unless you wish to be admitted to a psychiatric ward.