Agatha Christie's Poirot by ITV. I started checking out the books after watching the show, starting with an audiobook of Murder On The Orient Express, narrated by Kenneth Branagh.

Not exactly related to television, but you can tell that Branagh incorporated a lot more of the book into the movie than is immediately apparent, which I have to give the man credit for. Hearing his reading the book sounds almost like an early concept sketch for the entire film, from how he does a deep and gravelly voice for Ratchett to how near-identically he sounds to Josh Gad's MacQueen. They even manage to sneak in a reference to how Poirot managed to get onto the train as well and made it into an extra reference to Poirot loving Charles Dickens (if you didn't catch it, he >!caught onto the existence of a fake extra passenger because Hector MacQueen unknowingly referenced a Charles Dickens story; in the story he references, Mrs Harris isn't a real person but someone constantly referenced by another person so they can tell tall tales!<).