I've read the majority of the McNab production line and this is more of the same. The question isn't really whether this book is any good, but more, do you enjoy McNab books?
It tells a story of kids forced into fighting in Africa, scatters in a few morals, some revenge and a love interest. Standard fodder for McNab. The tale is fairly slow to start and there are some fairly obvious appearances later in the story, you can see them coming and it appears to be a trade off between continuity in the series of Stone tales and making the book stand on it's own merits.
If you like McNab, you'll like this, guns, violence and enough special forces references for armchair action fans. If you are new to McNab it's an engaging enough thriller with some page turning action / suspense sequences.
I've only given it three stars as whilst it's a readable story, it doesn't really break the mould and the stories are becoming a bit manufactured for my liking.