Having taken the MCAT twice I think that this book represents the real test better than anything else, INCLUDING the AAMC online exams. The passages/questions in this book reflect the recent shift toward micro-biology/genetics emphasis on the BS section, as well as to more experiment based passages. That said, I thought the VR passages on the two real MCATs were better than the AAMCs, but still not long enough when compared to the two real MCATs I've taken this year.
Also like others mentioned, their explanations of each question are very clear and helpful.