Although not different to the anime in content, the manga is the superior to the two.
I feel that the previous reviewer did not do this manga justice. 'Monster' is not just an incredible thriller, but is a compelling moral tale. Tenma is an expert neuro-surgeon with a promising future ahead of him. However, after his director instructs him to abandon his treatment of a Turkish worker (thus leaving this man to die) in order to perform a relatively minor opperation on a well known opera singer, he begins to see that his hospital is corrupt to the core and the people in positions of power do not believe that all men are created equal. Therefore, when Tenma is later ordered to stop operating on a boy with a serious head-wound in order to treat a richer client, he refuses to do so. This choice will set a series of events in motion which finally end several years later with Tenma as a wanted man, accused of several murders, and fleeing the police while trying to prove his innocence by revealing the true identity of a mysterous young man called Johann.
As I said before, Naoki Urasawa is a visionary. 'Monster' is so much more than just a thriller. It focuses on many moral implications such as whether or not one life is as valuable as another, the nature of choice and what it really is that makes a monster. On top of this is the historial aspects of the plot, as it is set mainly in Germany just after the fall of the Berlin Wall and does an incredible job of realistically presenting this time period.
I have been following this series since the first volume was released and have just finished reading volume 13. As this series is 18 volumes long, and so far has never lost its knack for keeping me enticed and excited since the first volume, I can honestly say that it is one of the best series's that I have ever read and could not recommend it more to anyone.