I read this book several years ago, when it first came out in paperback -- I knew very little at that time (not that I know much now) about Japan, and so cannot say how good it is. I have read some of the criticisms of it. It certainly made a persuasive case, so far as I could tell, against what was still the common view that Hirohito was merely an uninvolved cipher, who was used by the militarists and ultranationalists. According to Bix, Hirohito firmly controlled events by allowing his ministers to act - and that whenever they acted contrary to his desires, he would simply step in and divert them (or remove them). Hence, he fully bears the war guilt.
Dower speaks as if this question of Hirohito's pacificism and involvement is settled (and cites Bix). According to Dower, this image of the Emperor was a sham and a construction -- begun already pre-surrender by the likes of Shigemitsu with the aim of saving the throne (Shigemitsu believed that the reforms of the Occupation would eventually be undone, when the zaibatsu would be restored); and then adopted by MacArthur's "wedge policy" (derived from Bonner F. Fellers), which sought to drive a wedge between the militarists and the people by associating the Emperor with the latter: in other words, the Emperor and the people were good, and the "militarist gangsters" had betrayed them both.
This book is enormous -- but it read very quickly, for some reason. Maybe I didn't know enough to read it slowly.