I read it cover to cover prior to taking the exam and also ran through most of the test questions on the CD. As others have pointed out, the book by itself is not sufficient preparation for the exam. Some experience is a must (I was a MSSQL DBA ~3 years before taking the exam).
Taking the book purely on its own merit, it was very easy to read and digest and highlighted areas where I was weak. It links to a lot of online material, which I would recommend reading in addition.