It must have seemed like a good idea at the time, but somewhere between conception and execution Unbuilding unraveled. The drawings are, without a doubt, spectacular. The story is clever, but the love of the subject matter is missing. The story, at its most basic, is about the disassembly of the Empire State Building. The details of its existence, however, are nowhere to be found. There is, for example, no information on how many tons of steel were used; how many thousands of rivets. Missing too, are any explanations of mechanical systems such as how water was pumped to bathrooms one thousand feet off the ground, or how the elevators safely and efficiently carried their passengers up 85 stories.
My suspicion is that Unbuilding's weakness lies at its foundation. Organized disassembly just isn't as interesting as a construction project. To be fair to Mr. Macaulay, it's not a bad book. Certainly, if this were the first of his work that you had seen, you would be suitably impressed. But in the context of his efforts prior to and after this one, it fails to captivate. My advice is that, if you are collecting the series, you'll most certainly want Unbuilding. If, however, you are new to Macaulay's work, Castle, Cathedral, City and Mill are significantly better choices.