Absolute classic. A Must read.

The Tower and the Bridge: The New Art of Structural Engineering - David P. Billington

A classic! 

After reading this book I wanted to quit work and return to school to study civil engineering. Of course, I made the mistake of mentioning this to my wife, who fell into paroxysms of laughter, saying she had seen some of the stuff I had built at home, and there was no way she would ever go on a bridge that I designed. 

Billington discusses the interrelationship of efficiency, economy, and aesthetics and how great engineering works combine all three of these to the exclusion of none. The great designers manage to balance beauty with simplicity and cost. Frankly, I found this book riveting (pun intended, although he really celebrates the use of concrete as opposed to steel) and never fail to look carefully at bridges with a new eye.