The first thing you need to know is that this is not "Islam in 5 Easy Steps".
The truth is that for many Christians, Islam is mysterious, and it seems like a mountain of a task to engage with Muslims with any degree of success. Unlike so much of the material written by Christians on this topic, often full of sweeping generalisations based on secondary sources, this book is scholarly and the author's use of primary sources is very evident.
The book is quite technical in some places and includes a number of lengthy quotes from literature outside the Qur'an itself, which will no doubt put off casual readers. This approach is necessary however. The teachings of the Qur'an are clearly laid out in a systematic way, including their relevance to Christian - Muslim dialogue. The important differences between Christianity and Islam become increasingly clear as the book progresses, so that by the time you have finished reading it you are in a far better position to talk with your Muslim friends on a meaningful level, without simply talking past each other.
You'll be disappointed if you want a quick fix, or if you refuse to read the endnotes (containing some excellent information). If however, you want to truly understand Islam and how to approach the challenge of witnessing to Muslims then you will not find a better book anywhere. Especially useful is the information on the hadith literature.
A book that you will find yourself coming back to again and again to dig for more information. A truly excellent work, scholarly, respectful and readable.