This book was really helpful in getting to grips with how to use sass and compass. Covering everything from the basics of the sass syntax to authoring your own extensions, this book was clear, concise and well written. It is a shame that more programming books cannot be written in this fashion, with many instead aiming to be 'the complete guide to language x' resulting in 1000 page monstrosities that are too large to be practicable and too fastidious to be comprehensible.
Although most of the information contained in the book is no doubt available in the documentation, having practical examples of how, for instance, sass can help you use grid frameworks while still keeping your html semantic, was of great help in leading me to understand the important role that css preprocessors can play going forward. I was also totally unaware that compass could create css sprites until reading this book, and having such a tool integrated into the design workflow offers a way to increase site efficiency while not increasing the time spent on design.
Having read this book you can step firmly into building your CSS with Sass & Compass. You need to know CSS quite well in order to grasp it all and to see the difference of building it with Sass & Compass instead of by hand or using different tools. You'll have a chance of going through a different scenarios, all using the best development practices.