Pocket Ref

Find out what you need to know, when/where you need to know it with Pocket Ref by Thomas J. Glover ($10). This shirt pocket-sized, 768-page tome is filled with conversions, tables, maps, formulas, and other miscellaneous data for on-the-go reference. Plus, it's an actual book, so it's not limited to areas with solid cellular/Wi-Fi connections, unlike those electronic pocket reference thingys all the kids seem to carry around these days.