The Mythical Man-Month
The Mythical Man-Month is the book when it comes to software project management. In its nearly 20 years in print, it has defined how good managers approach not only software development, but all sorts of projects. In fact, over 250,000 copies are in print.
The 2nd Edition new material, including a retrospective, additional papers and more.
You can pick up the paperback here for $28, or download the Kindle version for $17.