You all already know that I’m a strong advocate of CSS Preprocessors and a big fan of Sass. If you still haven’t given Sass a chance now is the right time to do it. Pragmatic Guide to Sass will help you get started with it.
Although this book was published more than a year ago and it doesn’t cover some of the things that were introduced into Sass recently, it does an excellent job of explaining basic Sass concepts. It’ll teach you everything you need to know to be able to use Sass confidently in your day-to-day projects and it’ll make it easier for you to dig deeper into more advanced Sass techniques.
The book also does a good job of explaining Compass (which is one of the strongest sides of Sass if you ask me) and also gives a nice overview of HAML (HTML abstraction markup language).
All in all Pragmatic Guide to Sass is an excellent book that doesn’t go into great depths of Sass, but rather focuses on basics (which can be both good and bad, depending on your current knowledge).