Karen Traviss has done an excellent job with the Gears universe so far, and The Slab is no exception.
The story is one of the best yet, detailing Marcus' time in the infamous Slab. It's dark, gritty, and has an air of hopelessness to it even though those who've played the videogames know the best result.
The book is easy to read and follow. Fans of the videogames be warned, this is more of a character-driven story. There's action scenes (including a nice little nod to the first game at the end,) but most of the book focuses on the characters. I found no problem with this, however, and couldn't put it down until the end.
I would give the book five stars, but what's holding me back is one tiny thing; we are teased answers to two of the big questions left at the end of Gears of War 3, but not given them!!
All in all, a great read. Hoping for a sequel, set after Gears 3! Please Karen!!