I skimmed through the relevant chapters in this book several times before our holiday in South Africa. It's one of those books that don't make much sense until you get there. Once you are in the country it's useful as a reference guide and I use it to tick off places I've seen etc. I'm not sure it's useful to have so much detail of certain things, eg layouts of buildings and castles. It's very touristic and won't cover things that you experience whilst driving along and often you see something but it's not in the book. It also tends to push you to the tourist activities rather than see it yourself activities. For example, the referral to Boulders Beach Penguin Colony near Simon's Town was a hot spot of tourists, including a bunch of Japanese tour groups, and you had to pay to get in to see the Penguins. Instead if you drive 5 more min you can spot Penguins without tourists and having to pay. I'm all for exploring yourself without being told what to do by a book.
To summarise, useful when you arrive in South Africa to figure out what you have seen and what tourists like seeing.
Be aware that it doesn't contain useful maps for driving. You are better off buying one when you get to South Africa. Also, if you have an interest in animals and plants, get another book as this one won't cover flora and fauna.