I bought this book when I was starting out on the Alpha course. A lot of what is in the book is shown in Gumbel's speeches shown on the course, but the book allows time and space to go into more detail.
I found this book extremely helpful, comforting and thought-provoking as someone who is just adopting Christianity. It doesn't provide all the answers, which never could be answered anyway. But it does make you think and it makes you feel that someone really understands what you're going through as a new Christian, which can be a scary but ultimately wonderful time. Gumbel's anecdotes are funny and provide a lighter edge to what could be viewed as a 'heavy' subject matter.