I'm wanting to learn more about IL and CLR / DLR under the hood. A friend of mine recommended the book "Inside Microsoft .NET IL Assembler", but since it came out in 2002 I fear it's pretty out of date at this point.
Does anyone have any more up-to-date books or websites that can be used by someone who understands .NET languages to learn more about the inner workings of IL and the CLR?
I'd suggest you check out some of the more detailed chapters in CLR Via C# by Jeffrey Richter. It doesn't go into as much detail as you'd like probably, but its a good start and covers the 2.0 CLR and so is somewhat current through .NET 4.0.
For an interesting look at CLR low-level details I like SSCLI Essentials. Not so useful for IL / DLR.
You might check out a similiar question: What is your recommendation for a good book on the .NET CLR and CIL?
Perhaps my answer is a bit late now, but the book "MS Press - Inside Microsoft .NET IL Assembler" is actually excellent. Remember: framework 3.X only adds new classes and functionality. Underlying technology is still the same. So the book still stands, at least until FW3.5.
Side to side to ECMA, and some hard work, you have everything you need.