The Mysterious Affair at Styles
Hercule Poirot #1 is in the public Domain in the U.S.A.
http://www.feedbooks.com/list/3653/hercule-poirot
That's interesting. A shame it is probably the least entertaining of all her books.
I've read several of Christie's works and The Mysterious Affair at Styles was the only one I'd call dull.