Doctor Who: Every Tenth Doctor Episode Ranked From Worst To Best
2. Silence In The Library/Forest Of The Dead
Unsurprisingly for a Steven Moffat story, there are so many ingenious ideas in Silence in the Library/Forest of the Dead: a world that is a library, flesh-eating shadows, and a time-travelling archaeologist who claims to know the Doctor, but who he doesn't recognise. It's also a testament to Moffat's writing that we never feel bombarded with all of these elements, and none of them feel undercooked.
As per usual in Moffat's stories, the dialogue is witty, the action tense, and the finale emotional. In the 90 minute runtime there is not a single line wasted, and it could very easily (and enjoyably) be watched as a short film instead of two separate TV episodes.
It's also fascinating to go back and watch these episodes with the knowledge of River Song's arc in mind, as you gain an entirely new perspective on her interactions with the Doctor. Silence in the Library/Forest of the Dead is not only the start of the "Madame Kovarian's home-grown psychopath" arc, it can also be viewed as the start of the Amy Pond story too, and all these connections give the story even more weight than it had on broadcast.