The book adheres to their mantra less is more: it is only 273 pages, and about one third of them don’t contain text. The chapters are short and easy to read. You could read the whole book in an evening if you’d want (and then re-read it the evening after it).
The content is very much the same as svn, so in a way it was 16 euro thrown away. By following their blog, you could read pretty much the same. But when you look at it in another way: for just 16 euro, and very little of your time (which is still a lot more valuable than that 16 euro), you can read the insights of some pretty smart guys. Some of it are open doors, and you don’t have to agree on everything, but I’m sure everyone will get something useful out of it. And from that perspective, it’s a steal (even if you could subscribe to svn).