I agree with the other reviewers here about this book; it is indeed a "must-read". This book is not really a story of rugby, as later portrayed in the Hollywood movie; it is a story of a country struggling with a massive and long-overdue change in the fabric of its society.
John Carlin tells the story of South Africa during the transition period after Nelson Mandela was freed from prison and apartheid ended. Whether you are an expert in this era or a neophyte, Carlin's writing and summary of this time is nothing short of superb. He is able to tell the tale of how South Africa managed an almost incomprehensibly huge change in its society without warfare, which is an incredible feat. Carlin had worked in South Africa and as such had background knowledge of the country as well as access to the many prominent figures that he interviewed for the book, including Mandela himself.
The role of rugby in this book is as the thread that ties together the characters from all walks of life who appear throughout the story. It doesn't much resemble the movie in that sense, which relied more heavily on showing the rugby team, games, etc., as the primary driver of the story. The book is far more powerful.
Everyone, and I do mean everyone, should read this book. It is well-written, fast-paced, emotional, and tells a story that would have been unbelievable if it weren't true. As a side note, the poem "Invictus", for which the movie was titled, brilliantly captures the bravery of Mandela and all of South Africa shown in this book.
"It matters not how strait the gate,
How charged with punishments the scroll.
I am the master of my fate:
I am the captain of my soul."
Excerpt from Invictus, by William Ernest Henley