Earlier quoted context omitted.
You might want to read AMOP. It's not build out of macros, but a meta-object system. It also took a decade of research&development to develop CLOS + MOP. From Flavors and LOOPS to AMOP.
I've had it recommended to me before, but never read it. I also wasn't aware of the extreme effort in getting it right. Thank you.
http://ml.cddddr.org/cl-object-oriented-programming/
The repository spans from 1984 to 1990.
The group also developed a portable CLOS implementation (PCL, Portable Common Loops) to experiment and verify their design with feedback from the community:
https://www.cs.cmu.edu/Groups/AI/lang/lisp/oop/clos/pcl/0.ht...
Flavors and LOOPS were developed around 1980 and were the direct inspirations. The AMOP book was then published 1991.
AMOP is a very good and extremely well written book about the CLOS Meta Object Protocol.
It also is fortunately / unfortunately one of the books with the best Lisp programming style. 'fortunately' because it is really great, 'unfortunately' the great programming style is tied to a slightly esoteric topic - object-oriented meta-object protocols. ;-)
Whatever motivation you have, a) reading a book with great Lisp style or b) learning about the CLOS MOP, the book is highly recommended.