I finished reading Mythical Man Month (aka MMM) recently and quite honestly I was amazed at how a book that was originally published in 1975 can be so on target with so man aspects of software development. Obviously not everything in the book is so pertinent however his foresight is amazing. The MMM is in a nutshell about debunking the theory that if you add more people to a project then you can speed the project up in a linear manner. The book makes quite a bit of sense. When you add in communication factors, learning curves, and the other items Brooks brings to light in the book you quickly see where he is coming from. Funny thing is the place we are in software development now might also brings an additional factor to the table. Offshoring brings even more of a communication gap. Both time zone gaps and language differences come into play. But I digress. In truth, I think the book has survived this long because Brooks focused more on the human aspect of development than on the actual programming piece. People don't change quite as rapidly as software so it makes sense that the book would still be applicable in today's environment. People are still a limited and valuable resource and it will probably remain that way. (Moore's Law is there for machines but not for people.)
For managers, I think the book is must read. For everyone else, the book is easy reading so if you have time I would recommend you read it. The first 17 chapters of the anniversary edition are the most worthwhile. I think the other chapters are really him just defending himself against criticism and not really as important to read (but hell that leaves only 3 chapters and like I said it's easy reading).