I second @TJ Bakre's suggestion of Jeffrey Richter's fine book for really getting into the CLR. But, if you're looking for a wide-coverage book that also goes into some significant depth I can recommend C# 4.0 Unleashed as a way to get from basic familiarity with C# to prepare for the dive into the deeper levels treated by Richter and Skeet.
Note: While I understand the general prejudice against the Unleashed series that prompted @IAbstract (and now another) to punish me for my initial response, I do not believe he has fully examined this particular volume in the series. Bart De Smet frequently takes a feature of the most recent version of C# down to the CLR and gives a reader a way to move from an outer layer to the inner without requiring them to make the jump wholesale. Note that I did second the recommendation of Richter's book for the truly serious learner. As I read the OP's phrasing of the question, I formed a picture of someone who is trying to get to the point where Richter and Skeet can take over and lead them through the rest of the long journey towards a really deep understanding. Personally, I'm pretty deep in .NET and I still find some of De Smet's somewhat shallower dives to be useful to my understanding. I stand by my recommendation when taken as a connector to the other two recommendations.
Actually, though, I deserve to be "dissed" because the OP was asking for a single "canonical" source and I recommended something this side of that and did not actually answer the question as stated. My bad!