Doctor Who: The Eternity Clock is a decent co-op platformer with good puzzles made of simpler puzzles. The experience as a whole is like playing any other platformer here you can't kill enemies. You have to time your jumps, cooperatively solve puzzles that involve both characters, and collect all the hats (which you can't wear, go figure) and all the journal pages (which you can't read either).
The game features voice acting from original actors, and shows the Eleventh Doctor and River Song trying to solve a mystery. Nothing too far from normal telly episodes on the BBC, to be honest.
It's a good story, but it isn't enough. It's just fun for wasting some time or for when you have to wait your buddies to play an online game. It's worth its discount price but not more, and it's only for the diehard Doctor Who fan.