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.
First you get the list of nodes that are "/Books/Book", there are three nodes in that list. Then for each of them you get the first node that is "//Title/text()". Now in XPath "//" means "start at the root", so making that relative to one of the Book elements is pointless. If you had used "Title/text()" instead, that would have been relative to the Book element.