Instruct: Classify Amazon reviews into positive or negative sentiment
Query: A comprehensive, effective guide to interrelating at work

I really like and heavily rely on this book - it's a classic. It drives home the value of relating to the people who work for you (and around you) as a necessary component of getting work done. Then it goes, chapter by chapter, into the details of understanding your co-workers in terms of personality traits. Finally, it discusses essential interaction skills including listening skills, getting feedback, and using body language (there's more to it than you might think). I go back to this book again and again.