You can download these two sample chapters of the PowerPivot for Excel 2010: Give Your Data Meaning book:

  • Chapter 2 – PowerPivot at Work
    • This is introductive and suggested to read to anyone who is new to PowerPivot
  • Chapter 7 – Date Calculations in DAX
    • Do you want to make date calculation in DAX? This is the chapter for you: aggregations, comparisons, semiadditive measures, balance calculation by using transaction and much else.

Look at the download link in this page:

I suggest everyone to look at chapter 7 – date calculations in DAX are a very hot topic and many patterns are available and ready to use in that chapter!