As Banville spoke, he spotted a familiar face in the crowd...
John Banville, who wrote the introductions for the books, was the star turn of the evening and was interviewed by Fintan O'Toole before an audience of about 80 people who had turned up for the event in the Hub at TCD.
And who was sitting in the back row listening to Banville discussing Butler? Malcolm McArthur, that's who.
To say it added a certain frisson to the evening would be an understatement. The double murderer McArthur, on whom Banville based one of his best known novels, The Book of Evidence, appeared to be alone, although he did speak to people around him.
He was beautifully dressed, as ever, although a cravat had replaced the bow tie familiar from the press pictures of him after the killing spree in 1982 and the GUBU events that followed.
When the discussion was over, many of those present, including McArthur, stayed on for a drinks reception. Banville, however, left immediately.
Did the two meet before the public interview started? And if so, did they speak?
Banville said this week that he saw McArthur there, "large as life", but didn't talk to him.
He takes the view that McAethur has served his time (over 30 years) and now has a perfect right to go to any book launch he likes.
McArthur was released in September.
"His crimes were heinous, but he was kept in jail for what seemed an unjustifiably long time," Banville said.
"Meanwhile, there are people walking about freely in this country – some of them in Government or in parliament, north and south – who have the blood of hundreds if not thousands on their hands."
Hubert Butler, a Protestant and a minor ascendancy figure from Kilkenny who died in 1991, was probably the best of all Irish essayists.
He was widely travelled and wrote about many of the issues of his day as well as about leading lights from Irish literature and history.
In one of his introductions, Banville says Butler was "a vigorous thinker and a marvellous writer, one of those rare figures whose mild tone masks a steely resolve".
McArthur seems to be a fan of Butler.
One can only wonder what he thinks of The Book of Evidence. John Spain, Books Editor