My previous experience: I knew what (X)HTML was, but I'd never made a web page other than some rubbish at GCSE IT. I have been a C# programmer for 2-3 years, so I do have a general awareness of programming and mark-up languages.
The good: His explanations are clear, and with a good previous level of computer wisdom you will get to grips with the theory and power of CSS without having to read a section twice. (I can't really judge how this book would be for a complete beginner, but he certainly doesn't presume any previous knowledge so I would recommend this to a beginner.)
The bad:
As said in another review, he tells you how to use a text editor: "place your curser...", "press enter twice" etc. This is annoying and patronising if you know what you're doing.
He repeats himself over and over throughout each section. I must have been told what floating a block level element does over 5 times in different chapters.
His style of creating CSS sometimes conflicts with the whole purpose of CSS: To write HTML markup that is seperate from the layout/style. (e.g. He names classes after the position on the page they will be, something warned against in CSS Mastery)
I bought this for the Kindle, and the formatting of titles/sub-titles sometimes is a bit messed up. Still perfectly readable though.
Overall:
A very good book for learning CSS theory and techniques. It lost a star for repeating itself too much and therefore being a bit of a drag to finish.