While if you read my part 1 review you may know I liked it, but found it pales in comparison to the second part, Forest of the Dead. And it's ture - Silence in the Library plants the seeds of ideas while Forest of the Dead waters them, eagerly watches them grow in delight and finally shows them in their true, shining form. We discover the truth behind the strange little girl, the Vatsha Nerada, and the mysterious Doctor Moon, and we also find out more about River Song.
Part 2 also features one of the best sub-plots in all of Doctor Who - Donna trapped inside a computer world, which has been created perfectly for her conscious to live in. It's such a cool idea, and the scene where Donna realises her children aren't real while the sky goes red is an absolute favourite of mine.
The scenes in the Library are amazing too. Alex Kingston and David Tennant have great chemistry, and the setting is utilised so much better here, although, like the first part, I still don't really care about the supporting Archaeologists - though that dosen't matter as much, as the story is more focused on River and the Doctor.
The ending is so emotinial, with an absolutely amazing score by Murray Gold. It really is one of the best episodes of the show, and it's one all fans should watch. 10/10, one of Season 4's best.