He died on Thursday at the Mater. While his death is described as sudden, he had been suffering from cancer for some time and yet had recently cancelled at short notice a trip to the USA (where his memoir had received excellent reviews, such as in the Washington Post & New York Times). Unfortunately the bulk of the Irish Times tribute is behind subscription, so the Telegraph gets the head start with the accessible obituary, not least with an anecdote that the Telegraph would love:
Once, during a live television interview in Belfast, an Orangeman in the audience stood up and said: "Here is a man whose book has been banned by the papist government in the south, has been sacked by the Archbishop of Dublin and he comes up here to Belfast and praises the Catholic Church. Moscow couldn't have done a better job of brainwashing."
McGahern likely knew that time would vindicate his quiet dissent and at least he lived long enough to see it.
UPDATE: Times of London obit and RTE's report on the funeral.