Book On Web front End Optimization

I am currently reading a book "High Performance Websites" by Steve Souders. Its an excellent book which distills years of experience on optimizing websites.

I was quite surprised to learn that almost all websites spend 10-20% of the time performing the backend processing required to deliver the HTML content and the HTML page itself. The remaining 80% t0 90% is spent in downloading and rendering page components like images, css, scripts and so on. So if you want to optimize your websites start there.