When I first started working with AJAX... I got a book "Web 2.0" from Wrox Press... it was a few years old when I got it (found it in the computers section of my local Half-Priced Books store) so it would be even older now, but by reading through the first part of it how AJAX works, and some of the nitty gritty details... gave me a foundation upon which allowed me to understand how JQuery works, that it's nothing magical other than a collection of Javascript libraries that react to events in the browser, and allowed me to get going pretty quickly. I'd offer to ship it to you, but I've moved three times since then and have no idea where it is. It's helpful to understand events, functional programming, callbacks and how delegates work.

One of the nice things I like about most libraries is that you only need to load just the libraries that you need. If you don't need it, don't load it. It helps keep the pages lightweight.

-tg