I really think this book should be prefaced with a warning--if you DON'T want to be convicted about witnessing, don't read it!!
Mark Cahill is a wonderful communicator. This means his book is LOTS of fun to read--even if it's also painful to read. He deftly shows the reader the necessity of a Christian witnessing (it, quite simply, is non-optional for a Christfollower). He then proceeds to take all the usual excuses we give and show how they absolutely don't hold water. By the end of the book he has shown the imperitive necessity, removed any mental blocks/excuses, and armed the reader with an arsenal of ideas for ways to witness. He has chapters covering some of the most common questions that the unsaved have along with answers, and ideas for conversational lead-ins. This book is about as close as you will get to having a experienced "witnesser" hold your hand and walk you through the process. Definitely a must-read for any Christian (whether or not they are interested!! :P)