I like the Dummies and Idiots books. I think they’re great if you don’t know much about a subject and want to get an introduction to it.
I don’t know how easy this section would be to understand if you didn’t have a programming background, but I thought he explained everything clearly and with good examples. But I don’t think too many people without a programming background would be or should be reading a book that involves AJAX anyway.
The third part covers jQuery and AJAX. I was expecting a little more than two chapters about AJAX, but maybe more isn’t really necessary. After the first chapter in this section, he uses jQuery for all the examples. He mentions other JS libraries but recommends jQuery. I’ve “used” jQuery before, adding image galleries and things, but not modifying it or writing it myself. I was surprised at how easy it is to use jQuery and AJAX to interact with PHP.