A seminal book about structuring and managing large software projects subtitled "Essays on Software Engineering". Written by Frederick P. Brooks, Jr. Project manager for the development of the Operating System/360 for IBM. It was published in 1975 and still has much that is relevant even in current development environments. To a great extent this is the foundation upon which all later software development methodologies are based.
The Mythical Man-Month of the title refers to the spurious belief amongst some non-programming managers (PHB) that if it takes a programmer six-months to develop a module then six programmers could do the job in one month.