Okay, so calling the Pocket Ref an ultimate guide to everything may be an exaggeration, but not by as much as you might think. The Pocket Ref is packed full of indispensable information for construction workers, engineers, scientists, travelers, and pretty much everyone else.
While a majority of the book offers technical details, there are also many useful general-interest tidbits such as a chili pepper hotness scale, worldwide and USA telephone area codes, and a chart of average climate conditions for select US cities, just to name a few. Heck, it even gives you the keyboard codes for typing out σ, ☼, and ♫.
The Pocket Ref is one of my favorite gift ideas since it is as entertaining as it is affordable (about $10). I bought my first Pocket Ref several years ago and still learn something new everytime I flip through it.
You can browse parts of the book (mainly the Table of Contents and Index) via Amazon.