A good introduction to the 914 and the unfortunate corporate history surrounding it. This would actually be a very good case study for business managers contemplating corporate joint ventures. The book goes into great depth into why the 914 "failed", although the author does state that, at over 100K unit sales, the 914 was far from a failure.
However, the book does lack a lot of the detail readers may want surrounding the 914 itself. The author could have gone into a more detailed history surrounding the car's design, which is the core appeal of the 914 (e.g., there is no in depth account of the third-party company contracted to design the car).
In addition, while the book goes on to describe the 914's replacements at Porsche, it does not go into depth about how the design concepts embodied in the 914 were adapted and used in other vehicles that followed (e.g., Toyota's MR2, GM's Fiero, Porsche's Boxster, even Subaru, which still use flat fours).
Overall, this is a good book on the 914, but, if Mr. Long is listening, a design book remains to be written.