Frederick Brooks is the author of this masterpiece. I read this book 10 years or so ago and I think every professional, who manage groups of professionals engaged in software development, should read it.
It is focused over the Brooks’s law: “Adding manpower to a late software project makes it later”.
The unit of measure is an unrealistic man-month used to tell the story of the development of OS/360 at IBM. He had added more programmers (more man month) to a project falling behind schedule, a decision that he would later conclude had, counter-intuitively, delayed the project even further.
It is old but still extremely relevant.