Prime Directive was a good idea, but done from the wrong angle. Although, I still find it hard to believe that the Federation would crack down so hard on Kirk, Uhura, McCoy, Chekov, and Sulu, just for violating the Prime Directive - after all, they violated it in just about every other episode in the series.
This book is divided into three parts.
The first part, your given absolutely no clue to why the Enterprise senior staff has been blackballed. At the very least, it does gets you wondering.
In the second part, Kirk is relates the story of how it happened and what exactly went wrong. In my opinion, it was this second part that saved Prime Directive; I thought it was a very intriguing story. It gives the reader very interesting insight to how the Federation handles First Contact missions.
However, the last part - featuring the resolution - brought down the entire story. (Minor Spoiler Alert!) It started out slow - and then the ending was just plain ridiculous. The aliens who manipulated the accusations against the Enterprise for destroying the planet were plain and simply stupid. It ruined the ending, and therefore - to me at least - the whole book was tainted.
I respect the author team who wrote Prime Directive, and in certain instances you can see their Trek experience in the way the story is told, but just be prepared for a let down.