This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
XOM is a library for reading, altering and writing XML documents, but I'm sure its web site has told you that already. Not sure what you mean by "why is it important"? Who says it is? People who use it will probably think it important, those who don't probably won't.