I’ve configured AMI on my Asterisk 18.5.1.
I can surf on http://my_ip:8088/asterisk/static/ajamdemo.html, but on http://my_ip:8088/asterisk/static/config/cfgbasic.html, after proper logged in, I’ve an infinite loop; see the video below.
That version of the book is very old. There are newer versions, under the title Asterisk: The Definitive Guide, online, and even newer versions in print, although none are really up to date.