One great argument of McGowan is that inerracy is a modern response to liberal theology and it's drive for rationalistic proof. Inerracy, claims McGowan, gives into the same rationalism that it reacts to (fights against). God cannot be captured by rationalistic arguments
Infallibility is a better doctrine because it doesn't tie God down to a mechanical understanding of inspiration. It is concerned with the ability of Scripture to be sufficient and efficient (Calvin) for salvation; in other words, God gets His message across in Scripture without being dependent on textual errors. Secondarily, it confirms the important role of the Holy Spirit in the development of Scripture in a way that the inerrant doctrine does not.
Great book with a lot of great historical stuff as well as suggestions for the use of Scripture in the everyday life of the church.