Naturally it's an idea to play the game this is based on once you have read the book, but even if you get hold of it after it's still not so bad. Obviously, if you've never played the game and never will (it's an Xbox game) then you shouldn't be reading this.
The book takes place in the same time frame as the game itself, and details the exploits of Tex, Hawk and Flint (no Brutus, you don't meet him until you're in the game) and the operations they conduct prior to their latest missions. In some ways the cut-scenes in the game belie the activities in the book, but it's a minor detail, the cut and thrust is there.
I expected this book to be trashy and not worth paying for - after all, they gave it away free with the game and it's not the longest book ever (more of a novella than a novel), but having been through it now I want more and can't wait for the post-game entries to be written! It's a very well written piece, fleshing out info you won't find in the game and giving a very frank and well-realised detail to the characters and situations they find themselves in. It is *NOT* a by-the-numbers, 'let's get them in there, make them shoot a few people and then get them out' book - it has some behind the scenes political aspects, and is very thrilling. Without ruining the plot, it has some major twists too.
Believe me, if you have the game you won't regret this buy.
The only reason it didn't make 5 stars was the length, and it is a prequal after all. And this from someone who has never read a game tie-in book and who doesn't like military novels or sci-fi books...!