I agree that John Allen’s book was incredibly useful 40 years ago to explain some of the nitty-gritty of implementing Lisp languages, but I can’t really recommend it today. The Genius of Lisp is fun and entertaining - something that I would recommend for the modern reader who wants material on the essence of Lisp languages with interesting history.

Adding it to the bibliography would be great, I just didn’t like the idea of someone seeing your comment, ordering a used copy of the very old Allen book and not enjoying it.