This is an awesome book, and I highly recommend it. Just be aware that very little of the book concerns itself with C. The majority of the book is an excellent tour of the internals of the Ruby interpreter.

Also of interest might be this series of blog posts currently being written: Reconstructing Ruby in C [0]

[0] http://www.halogenandtoast.com/reconstructing-ruby-our-first...

That's a great book -- highly recommended. But there's plenty more ground to cover!

Thank you. I just found that that title is included in O'Reilly's Safari.