Machine Man by Max Barry
Charles Neumann is not a people person. He's a scientific engineer at Better Future, a high-tech research and development company that develops and tests cutting-edge technologies and products, and he's more comfortable interacting with things containing a hard drive and power source than he is with things containing a brain and heart.
One day at work, in a moment of inattention, Charlie loses his leg when he gets too close to a hydraulic clamp moments before it shuts. The prosthetics he has to choose from leave a lot to be desired by his standards of efficiency and functionality, so he sets out to design and build a better leg. The leg he develops is far superior to even the best currently available to amputees, but he soon realizes that he will always be limited, not by his artificial leg anymore, but by his biological one. But that's a problem he can fix.
The book is pretty good. It has elements of my favorite genres: science fiction, horror, and thriller in it and Barry uses dark humor to counterbalance the implausibility of Charlie's gradual transformation. Machine Man isn't as good as the other book of his I read Company, but it's still a worthwhile read.
★ ★ ★ ☆ ☆