After many years of working with people who use Excel, I came to realize what they tend to want MOST so I created a special workbook entitled "Excel for Non-Dummies" (a take-off of the popular book series.)
I started putting in separate worksheets, each sheet carefully detailing a specific, relevant TIP, TRICK, or TECHNIQUE (TTT's.) What began with just a few worksheets has grown over the years to well over 100 sheets. An easy-to-navigate series of menus makes it very easy for the user to go directly to the TTT of interest.
Excel for Non-Dummies compiles thousands of hours of knowledge gained over years of working with Excel and Excel users at every skill level; it contains the most sought-after features and techniques needed for business, analysis, planning, and number-crunching purposes. These TTT's are all highly-documented in an easy-to-understand manner such that you will be able to put them into practice right away.
These TTT's are not esoteric examples that would be of interest only to astrophysicists and statisticians; there is a wealth of information that solves commonly-used problems in the real world. Maybe you won't be interested in all 112 TTT's but there is little doubt that some of them could very well save you significant time and trouble when using Excel.
Click the image link above to see all the TTT's available.