The added chapters contain (1) a crisp condensation of all the propositions asserted in the original book, including Brooks' central argument in The Mythical Man-Month: that large programming projects suffer management problems different from small ones due to the division of labor; that the conceptual integrity of the product is therefore critical; and that it is difficult but possible to achieve this unity; (2) Brooks' view of these propositions a generation later; (3) a reprint of his classic 1986 paper "No Silver Bullet"; and (4) today's thoughts on the 1986 assertion, "There will be no silver bullet within ten years."
The Odyssey is the story (a collection of short stories, really) about how King Odysseus and his men returned home after the Trojan War. It should have taken about a month for the king and his men to sail back to the kingdom of Ithaca, which was on the far side of Greece from the town of Troy. But it took Odysseus ten years to make the trip! That's how much trouble he ran into on the way. That's what happens, King Odysseus, finally realized, when you do not give the ancient Greek gods the respect they expect.
Agile processes promote sustainable development. The sponsors, developers, and users should be able to maintain a constant pace indefinitely . Just like you can't sprint for an entire marathon, you can't successfully develop software by forcing people to work overtime for months at a time. My experience is that you can only do high-quality, intellectual work for 5-6 hours a day before burning yourself out. Yes, the rest of the day can be filled up with email, meetings, water cooler discussions, and so on, but people's ability to do "real work" is limited. Yes, you might be able to do high-quality work for 12 hours a day, and do so for a few days straight, but after awhile you become exhausted and all you accomplish is 12 hours of mediocre work a day.