Although the name of the concept "serious games" sounds strange and evokes some debate, it is broadly accepted as a those games that are not intended for entertainment (alone), like games for education and training. The author takes it even broader and includes games-for-marketing-purposes also into this category. Almost implicitly serious games are computer-supported games, video games for short. Part of the argumentation in the book applies to non-computer games as well, however.
For those who are new in this field and for those who have their roots mainly in non-computer games, the book offers a broad overview of what is going on at this moment: examples in different sectors (certainly not education alone), possibilities, underlying software, the way of organising development projects, funding, best practices etc. If you are a specialist on one of these topics you may find its treatment too simple. For topics you are not a specialist on, the book offers a valuable introduction and overview, accompanied by numerous references and interesting links. The only thing I missed was an accompanying DVD crowded with demo software, white papers, clickable links etc.
As serious gaming seems to be hyping at the moment, the book was published just in time. The book is full of actual information. Therefore it is very useful NOW, although you may expect it to become out-of-date within a few years.