Interesting book about how to increase the performance of your code, each chapter is written by developer who worked on real project, who had to made an existing system faster.
They cover different goals, but what they have in common is a detailed understanding of what actually happens when, and how the different parts of large applications fit together.
olimex 
Oct 24, 2013 @ 09:34:17
I think you made a mistake, because in the page it says “buy xxx”, so is not free 😛
Oct 24, 2013 @ 09:36:02
Damn it, I just notice that you can click every section and read it.
Oct 24, 2013 @ 09:36:32
you can read online, if you want paper copy you buy it so yes, it’s free and you still can buy it if you want 🙂
Oct 24, 2013 @ 10:00:57
Wow, blazing fast! Right now budget is low, so I’ll keep reading the online version 😉