It actually does a really good job at adhering to canon. Not all of it made it in (I reckon they couldn't work out a way to fit in Norse gods having temper tantrums), and some of it did get shuffled about a bit, but it's very much what it should have been. :D

And while trying to avoid spoilers, I will say this: when watching this week's episode, keep in mind that they would have been filming at roughly the same time as Sherlock, making some things rather astoundingly coincidental. Appropriately enough.