The Art of the Metaobject Protocol
Anyone read it? The name keeps popping up for me in various places. Oddly enough, it was even mentioned in an annotated version of the CLI standard I was flipping through a few weeks ago.
For the uninitiated, it details the MOP behind Lisp’s CLOS. You can also find MOPs in Groovy and Ruby.
Googling brings back some very interesting reads.