Scrum: The Art of Doing Twice the Work in Half the Time by Jeff Sutherland.
You’ll get an overview of how the Agile methodology called Scrum works and examples of how it can be applied in this book. After reading this, Scrum became my preferred method of satisfying customer requests. The book also shows you how Scrum can be applied outside of I.T. If your department still believes not delivering anything until the project is 100% complete, i.e. the waterfall methodology, lend them this book.