Sterman has produced a very comprehensive introduction to System Dynamics (SD) modelling for primarily business executives (or students in non-quantitative education programs). It is well written, will keep the reader engaged with both the style and examples and is relatively easy to digest. Little to no background in advanced maths is necessary to follow it or construct the examples mentioned and explained in the book (and provided on the accompanying CD).
The book follows most basic building blocks that should be included in an introductory SD course and I found it quite useful in that context. The only real gap in such a use is that the space and attention devoted to validation of SD models are somewhat lacking, at least when compared to the other parts of the book.
If, however you have a more quantitative background (maths, physics, engineering, etc.) many of the concepts will be familiar and then the book becomes more of a 'flick through' guide. The response from such users I have encountered was that it is often considered relatively basic.
On top of that even a complete knowledge of the modelling concepts and approaches contained within will hardly make you anything but a novice when it comes to real SD modelling. Attempting to try and model real business problems with only the knowledge acquired in the book is more likely to lead to disaster than real insight - for that to happen some comprehensive further training / coaching is required - potentially explaining the relatively slow spread of SD in the business world.
Finally none of that should detract from the really important work Sterman has done in the field of SD by writing this comprehensive work and everyone working in the field is well advised to keep a copy at hand.