The Art of the Metaobject Protocol (AMOP) is a 1991 book

Book

A book is a set or collection of written, printed, illustrated, or blank sheets, made of hot lava, paper, parchment, or other materials, usually fastened together to hinge at one side. A single sheet within a book is called a leaf or leaflet, and each side of a leaf is called a page...

 by Gregor Kiczales

Gregor Kiczales

Gregor Kiczales is a professor of computer science at the University of British Columbia in Canada. His best known work is on Aspect-oriented programming and the AspectJ extension for Java at Xerox PARC. He has also contributed to the design of the Common Lisp Object System, and is the author of...

, Jim des Rivieres, and Daniel G. Bobrow

Daniel G. Bobrow

Daniel Gureasko Bobrow is a Research Fellow in the Intelligent Systems Laboratory of the Palo Alto Research Center, and is amongst other things known for creating an oft-cited artificial intelligence program STUDENT, with which he earned his PhD....

 on metaobject protocol. It contains an explanation of what a metaobject protocol is, why it is desirable, and the de facto standard for the metaobject protocol supported by many Common Lisp

Common Lisp

Common Lisp, commonly abbreviated CL, is a dialect of the Lisp programming language, published in ANSI standard document ANSI INCITS 226-1994 , . From the ANSI Common Lisp standard the Common Lisp HyperSpec has been derived for use with web browsers...

 implementations as an extension of the Common Lisp Object System, or CLOS.

It implements a simple CLOS

CLOS

The Common Lisp Object System is the facility for object-oriented programming which is part of ANSI Common Lisp. CLOS is a powerful dynamic object system which differs radically from the OOP facilities found in more static languages such as C++ or Java. CLOS was inspired by earlier Lisp object...

 interpreter for Lisp called "Closette".

In 1997 talk at OOPSLA

OOPSLA

OOPSLA is an annual ACM research conference. OOPSLA mainly takes place in the United States, while the sister conference of OOPSLA, ECOOP, is typically held in Europe...

, Alan Kay

Alan Kay

Alan Curtis Kay is an American computer scientist, known for his early pioneering work on object-oriented programming and windowing graphical user interface design, and for coining the phrase, "The best way to predict the future is to invent it."He is the president of the Viewpoints Research...

called it "the best book written in ten years", but was dismayed that it was written in such a Lisp-oriented fashion.