Books on Excel
You can buy any of the books below by clicking on its Amazon [affiliate] link.
The older books can be picked up at a Half-Price Bookstore, but make sure the CD disk is attached inside the back flap because it contains example files and an electronic version of the book.
Excel 2010 Bible
Excel Dashboards & Reports
Excel 2010 Tips & Tricks
Excel 2010 Formulas
Excel 2010 Power Programming with VBA
Excel 2003 Inside Out