Boooooooring
TL;DR: The Parthenon is important. It has columns. People came along many centuries later who also liked columns. People don't like columns as much now.
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I can see lots of people reviewing below that mention they thought this book would nod slightly more to the technical considerations of architecture (the maths and engineering etc.) rather than the philosophy of the discipline. Well I have to respectfully disagree, because I don't think the book really does either. I would have loved to learn more about either of those aspects but the sole purpose of this book seems to be listing off notable (predominantly Western) buildings, describing who built them and what they look like. I know this is A Very Short Introduction, but my god, this feels like a very superficial introduction.
Example in point, from the chapter (ironically titled) 'Buildings have meaning':
'...The meaning of medieval buildings has undergone the most extraordinary shift over the years. The most spectacular buildings of the medieval age are the great French cathedrals, such as Bourges, which were made so as to appear as if they were constructed out of little more than coloured light. Complex and ingenious arrangements of stone made this possible... blah blah BLAH...'
At no point does Mr Ballantyne stop to explain why the french cathedral builders designed the building in this way, what ideas inspired this design, in essence what was the meaning of the architecture to them. Nor does he attempt to explain what it might mean now (admittedly a much trickier question). He just describes the buildings at great length, then goes on to explain how the buildings and various features have fallen in and out of favour to present day. There's nothing meaningful in it.
Throughout this book I kept asking myself the same question: Why? Why did these architects design these grand buildings as they did? Why did later architects seek to emulate them? What did these buildings mean to the people who designed them? What was the theory or the ideas that informed the praxis?
To some extent even the descriptions felt superficial. Given the highly descriptive nature of the book, I was at least expecting a description of the key features of architectural movements. Ballantyne talks at great length about Gothic, Neoclassical, Romanesque, Baroque etc, but doesn't really attempt to pin down what these mean, he just describes more examples.
I feel like I don't need to cover this in any great detail as it has already been mentioned by others, but obviously the book is very focused on the West and this harms the objective to provide a very short introduction to architecture. I feel that if Ballantyne had attempted a more global outlook it might have forced him to answer a few more of the 'why's instead of just describing buildings. I also thought it was pretty elitist to describe the architect of the Pyramid of Giza, the Pantheon and Maison Carrée as 'unknown' or 'anonymous', whilst he described the traditional cottage in Figure 2 as having 'no architect'. Why? Someone clearly thought of it, was influenced by the culture around them, designed it and saw those plans realised.
As you will infer from the above, I generally felt quite frustrated reading this and at times bored. I will look out for some other books on the subject to compare.
...and just to reiterate: The Parthenon is important. It has columns. People came along many centuries later who also liked columns. People don't like columns as much now.