Fawcette Technical Publications has made a chapter of its new book
I read the chapter and its seems thorough enough to be useful. I have not read the book.
Tom Morrison
Understanding AJAX: Using JavaScript to Create Rich Internet Applications
available online here. The chapter is titled "Getting Started" and, to quote the blurb, "introduces you to the XMLHttpRequest object, showing you how to work around its implementation differences between browsers." I read the chapter and its seems thorough enough to be useful. I have not read the book.
Tom Morrison