O Natal de Poirot

It was a quick read that made me think hard on would be the killer. I figure it out that Pilar was not who we were told she was. But I never would figure it out who the killer was.
Poor characterization (comparing with Ten Little Niggers or Murder in the Orient Express) and it was hard to me to keep tracking who was who, or even trying to guessing who might be the killer because they were weak characters with the exception of Alfred, Harry, Stephen and Pilar.