I recently acquired this book for purposes of review and recommendation for Office 2007 literature at work.
John Walkenbach has written many books on the subject of Excel. As such, this book is comprised of summaries of several of his other, more specific publications.
Part 1 of the book goes over spreadsheet basics. This includes working with tables, which is a new Excel feature in 2007. You'll find most information pertinent to basic Excel usage in this section, and will be well on your way.
Part 2 is a summary of J.Walk's Excel 2007 formulas book. It includes the same basic chapters - Text, Date/Time, Count/Sum, Lookup, Financial, and two chapters on Array Formulas. If you already have the formulas book, this is completely useless; if you do not, this is a good overview without the extra details.
Part 3 is a short summary of the Excel 2003 charts and graphs, updated for Excel 2007. It also includes a section on working with graphics and the new conditional formatting features of Excel 2007. The information here is not terribly deep, but gives the basics of working with charts and provides some tips for advanced manipulation that is possible. The chapter on conditional is quite short, considering the number of improvements to this feature that has come about with Excel 2007.
Part 4 is a "miscellaneous" section, encompassing various features such as custom number formats, sharing Excel data, and a number of tips/tricks. Again, many of the features described are given an overview rather than an in-depth treatment, but I found that the essential features are all present and accounted for. There is also some information for working in a networked environment and with the Internet.
Part V deals with data analysis, for operations contained on the Data tab of the Excel 2007 ribbon. Most notably, there is a chapter on using MS Query, and two chapters about pivot tables. Part V also covers Goal Seek and Solver, and provides an overview of the tools included with the Analysis ToolPak. This exposes the reader to the features, but does not provide a whole lot of examples, although J.Walk's examples do tend to showcase just how far you can take some of the Excel features.
Finally, Part VI is a (very brief) summary of Excel 2007 Power Programming. It covers custom user-defined worksheet functions, user forms, and workbook events. There is also a number of examples of code that's readily useable in your own projects and Excel-based solutions. This section is enough to get you started, particularly if you have some programming experience, but if you want to get serious with VBA, this will only get your foot in the door.
Overall, this book is perfect for beginners and intermediate users who do not have a lifetime to devote to Excel. Granted, this book is pretty long, but as I mentioned throughout, it's to the point and not excessively verbose. I think of it as an extended tutorial walkthrough of the different Excel functionality. It does not include case studies or exhaustive spreadsheet solution examples. For advanced users, a vast majority of chapters will be unnecessary.