Finally I'm recovering some free time, so I'm going back to reading tech books.
This O'Reilly book about scalability I had pending to read since months, so having just finished it today.
Review
Title: Building Scalable Websites
Author: Cal Henderson
Starts with a basic but good introduction: Build layered code, separation of concerns, interface definition (broader one, not based on a programming language).
There are chapters about hardware, networking, capacity planning... Almost every high scalability concept has at least a mention and usually best practices.
The book goes directly to the point, throwing you constant, multiple examples of what's the problem, what can it cause and how to mitigate, solve and prevent it. For once, is a book where examples serve as theory instead of clarification or redundancy.
HTML filtering and web security basics are some semi-unrelated topics also explained here, like email sending tricks and best practices. They are not bad in themselves but really not about scalability, and that's my main negative point. We're here to talk about scalability, not about "miscellaneous tricks”.
Going asyncronous, building and communicating services (mainly http+XML)… last chapters go too far with systems, with so much content about load balancing, networking, and other topics that while are ok, is not purely development.
Final chapters go back to scalability, with how to do mysql vertical and horizontal scaling, federation, clustering... stats & metrics, API design (at a basic level, a few nice tips but very poor in general).
Concluding, a good book but mixed bag of topics. Some of them are probably to fill pages, but still the book has good advices and basic teachings for building a scalable website.