As noted below, TheServerSide.net is providing a free download (single PDF in an 8.82 MB ZIP) of Essential XML Reference, courtesy of DevelopMentor. Note: Free registration on TheServerSide.net is required prior to download.
Developmentor has exlusively provided TheServerSide.com with the entire book of Essential XML Quick Reference for free download. Essential XML Quick Reference is for anyone working with today's mainstream XML technologies. It was specifically designed to serve as a handy but thorough quick reference that answers the most common XML-related technical questions.It goes beyond the traditional pocket reference design by providing complete coverage of each topic along with plenty of meaningful examples. Each chapter provides a brief introduction, which is followed by the detailed reference information. This approach assumes the reader has a basic understanding of the given topic.The detailed outline (at the beginning), index (in the back), bleeding tabs (along the side), and the page headers/footers were designed to help readers quickly find answers to their questions.
By way of Brian Ritchie's Blog.