Well, it was 1983. So seeing something like this in a programming language was more novel than it is now. Also, up to that point the author has only programmed

Well, it was 1983. So seeing something like this in a programming language was more novel than it is now. Also, up to that point the author has only programmed in a couple of different assembly languages, plus Basic. Coming at it from that perspective, there's plenty of novelty to be found in Lisp family languages.