...first published in the UK by the Collins Crime Club in November 1939 under the title of Ten Little Niggers  and in US by Dodd, Mead and Company in 1940 under the title of And Then There Were None.
Not only that:
As the years passed by and gradually went out of style, many of the earlier remarks were edited from [Agatha Christie's] mysteries and more acceptable passages used to replace them.
I should say that Christie wrote more than 80 detective novels in her long career, and I must have read about 50 of them from between the time I was 15 to the time I moved out of the house (mom and I used to buy them at the local book exchange and swap them back and forth). I don't remember anything at all racist in them, but perhaps I was getting the later, cleaned-up editions. Interestingly enough (maybe), the same process of retroactive censorship was applied to The Hardy Boys series. The first books (about pre 1960, lets say) contained language similar to Christie's, which got expunged from succeeding editions. I also remember that in one of them a dog belonging to the villain is shot. Happily, in later versions, the dog is allowed to run free.
Looking back on some of the other material that I encountered as a child, I kind of sensed that the underlying Colonial politics of Babar were pretty doubtful, and my first encounter of the Tin Tin stories were in their serialized forms in kids magazines, so I don't know if these were the more or less prettied up versions that followed. I do remember reading "Tin Tin in the Congo", though, which was one of the books in that series that got creator Georges Prosper Remi (Hergé) in a certain amount of trouble recently. I don't remember thinking twice about it at all.
And, as for the Lakota Board's decision, well I suppose its up to them. But I'm not sure how the material can still be offensive if performed under one of the newer titles. And while Christie's novels are not high literature, they are hardly disposable public art, either. For example, "The Murder of Roger Ackroyd" is structurally innovative and heavily influenced the mystery genre, although when originally published many people felt the twist ending was a cheat. If the Jewish community has historically been able to get their heads around Antonio in The Merchant of Venice or Barabas in The Jew Of Malta, then you would think the folks at Lakota would be able to handle a bowdlerized version of Agatha Christie.