Calyn replied:
My all time favorite story/episode of Doctor Who is Silence in the Library. I've only watched 9-11 but that's definitely my favorite. Despite it being incredibly creepy (which I love) it was super cool how that was the first we saw River and it was her death. Loved it.That's one of my favorite Tenth Doctor adventures as well.
I don't think the nonlinear possibilities of time travelers was explored very much before River. At least not on screen. It's honestly just a fun thing to see.
One part of the episode that I like is how The Doctor refers to his future self in it. There's a scene between River's death and her upload into the Library that I'm thinking of specifically.
In reference to River's sonic, Ten says that "He" gave it to her. The Doctor looks at the thought process of the future Doctor in the third person, but near the end of his deduction, when he's discovering the purpose of the screwdriver, he switches to "I."
It's just a subtle inguistic choice to show how his regard for River is changing. Before that, she was someone he'd just met and didn't necessarily mean anything special, but the I shows that he's grown fond of her to some degree, though certainly not as far as he one day would. But the I is what placed River into his present, rather than his future.
