I was a bit disappointed. I'm not a beginner nor an expert. Some technical books give you something that you get energised about, and want to go try straight away; unfortunately I didn't get anything useful from this book, and only slight inspiration.
On the plus side, it is well written and laid out, has a nice informal air.
For example, this is not for you if you already know about the differences between GIF, JPG and PNG; or if you know a bit about colour wheels and complementary colours; or if you are familiar with web-safe fonts.
Fine for beginners and a little bit after that. Not really for semi-pros onwards.