There is a newer edition of this book:
Microsoft Excel 2013: Building Data Models with PowerPivot

Transform your skills, data, and business—with the power user’s guide to PowerPivot for Excel. Led by two Business Intelligence (BI) experts, you will learn how to create and share your own BI solutions using software you already know and love: Microsoft Excel.

Discover how to extend your existing skills, using the PowerPivot add-in to quickly turn mass quantities of data into meaningful information and on-the-job results—no programming required.

The book introduces you to PowerPivot functionality and takes a pragmatic approach to understanding and working with data models, data loading, data manipulation with Data Analysis Expressions (DAX), simple-to-sophisticated calculations, what-if analysis, and PowerPivot patterns. Learn how to create your own “self-service” BI solutions, and then share your results effortlessly across your organization using Microsoft SharePoint.

Sample chapters

Download the sample chapters of the book from here:   PowerPivot-for-Excel2010-SampleChapters.pdf