I recently went travelling in South Africa, Zimbabwe and Botswana and took this book with me as well as a book for South Africa, which was an older edition.
I actually found that a common talking point for many travellers when I was down there was how useless the Southern Africa guide was. This book is essentially cobbled together out of other Lonely planet books so some of the information is very much out of date, especially in Zimbabwe. I even met one couple who said that they went to an establishment mentioned in this guide, and learned that lonely planet had not in fact visited for ten years. Even the reviews of Accommodation etc. were hit and miss, not to mention the prices. And I have had some very bad experiences with the maps (especially in Vic Falls!), so make sure if you are driving you also buy a road atlas for finding your place to stay.
Although it must be admitted that Africa is constantly changing when it comes to small business, I would highly recommend taking what is said in the book with a pinch of salt. However, when it comes down to places to see, etc. the guide is very handy. Just remember that what is written prices, accommodation and places to eat, etc. must not be taken as gospel - if you are after such detail you are much better off buying guides for individual countries and always double checking on the internet.
I know that it doesn't seem that useful suggesting that you buy all these individual country guides and atlases, and it would be wonderful if this book was as good as you want it to be, but the fact remains that you cannot place that much faith in a book that seeks to sum up such a huge and diverse area such as Southern Africa in such a small publication, unless it is going to be updated every year.
That said people have had good experiences with this guide so by all means buy it if it works for where you're off to and use it as a means of searching for inspiration - But I just didn't think it compares with the quality European guides, for example.
Best of luck to anyone about to embark on an African adventure - it really is an amazing place.
P.S. GO TO ZIMBABWE.