Phillip Johnson introduced the "intelligent design" movement in his other books: Darwin on Trial, Defeating Darwinism by Opening Minds, and Reason in the Balance. Intelligent design arguments are the "wedge" that seems capable of breaking open the Darwinian stronghold.
Johnson has spearheaded a growing group of Christian scientists, philosophers, and others who have taken the battle into the public square. They've gained more ground in a few years than those using Genesis-based arguments have accomplished in decades. This book recounts the ongoing battle and the critical arguments and positions--almost like keeping us posted on the moves in a chess game. However, this book goes beyond the present debate to describe where the arguments need to go next--dealing with the identity of the intelligent designer.
Those who want to be serious contenders in the "origins" debate really must stay apprised of the "Wedge" activities. These folks are learning how to present the questions and challenges to Darwinian naturalism in such a way that the scientific world is beginning to sit up and take notice. Phillip Johnson deserves a great deal of credit for outlining the path for the debate by developing a broad strategy that is then fed by the work of other Wedge members who supply the scientific research and analysis necessary to make the strongest arguments. While this book is helpful, it would be better to start with any of his other books (especially Darwin on Trial) first to understand the background of The Wedge of Truth.