I found this great PowerPoint presentation done by Jason Whittington last year called Inside Rotor - Poking at the SSCLI for fun and profit. I found it as part of this set of older wiki links for the Rotor infrastructure.
I have noted in various places (probably old links from a year ago) that Peter Drayton and Jason were collaborating on a book called “CLR Internals“. Is that still in the works? Or is that project put on hold? Does anyone know?