David Suchet, who is himself of Jewish ancestry and raised without religion, came to Christianity at the age of 40. You can clearly see the influence of this in the very Christian tone of the later Poirot series and it was those works that led me to this one.
This documentary provides a very good summary of the life and works of Peter without the usual hateful, atheist revisionism that you might expect from a BBC or PBS documentary on the same subject. I recommend this this both to provide a good historical background on Peter as well as for the simple joy of spending more time with the wonderful David Suchet.