I read "Why Buildings Fall Down" by the same author a decade ago. This is actually the better book!
It's the engineering of buildings, as described by an architect. The architect in question is actually pretty snooty about structural engineers, perhaps to counter for the fact that they're spending so much time talking about structural engineering questions. The book describes engineering principles, illustrated by famous buildings (such as the Eiffel tower and Brooklyn Bridge). Quite frankly, I found that fascinating.
It's also a book of its time. Written in 1980, it's surprising to see quite how much things have changed. You can see what the trendy things of the day were. Apparently the future of architecture was going to be plastic. And maybe inflated domes.
So between the retro-ness and the architect's need to be an insightful polymath (there's a chapter on the semiotics of structure!), there's a lot of amusement. Combined with learning all about construction materials, and how buildings carry static and dynamic loads... it's actually something of an awesome book. Better than the sequel. :)