The author is/was working for Twitter. They are one of the first large scale web companies to adopt Scala. All the code works and their code has taught me much about sophisticated and clean programming style. Type less and do more and how it can support concurrency and scalability is thoroughly discussed in this book. Scala is not an easy language because of its rich syntax and its power and cleanness. The book is especially helpful to advanced users due to this nature. However, as for a beginner like me, I still find it immensely helpful. If you are experienced programmers, this is a good book for you. As for me, I want to use Scala to build my web application, this book is a good first step for me to take this route. To go further, I need additional references to help me achieve this goal. This is my first review and an expression of my gratitude to the author.