I apologize if this has been asked on this list before (I did a quick
search using Namazu and didn't find any specific books; perhaps that's
because they don't exist):

Are there any good books on domain specific languages (preferably in
Ruby)?  I've read Fowler's article on DSLs, I attended Glenn
Vanderburg's "Metaprogramming Ruby" talk at OSCON, I also listened to
Rich Kilmer speak at a NoVARUG meeting about a DSL he wrote for the
USAF/BBN and I've listened to the recording of Domain Specific
Languages by Jim Weirich from RubyConf 2005 -- but I still don't "get"
it. It seems like black magic to me, so I'm hoping there's a book out
there devoted to implementing DSLs using Ruby that can help me better
understand this useful technique.

Does anyone know of such a book?

Many thanks in advance,
Sean