If you are not watching it already, a) Poirot has been running off and on for 25! years, where have you been? b ) it is based on the books of Agatha Christie, a.k.a one of the best writers ever. So start immediately. The last two episodes ever are on the PBS website and you can find the other seasons on DVD. If I can't convince you, I hope my crappy caps will.
Feast your eyes on the gorgeous 30s/40s costuming.