In my opinion Ogilvy managed to write a classic with this one. The book is a good combination of advice about an advertising agency, running a professional services firm, the advertising business overall, as well as a really entertaining read.
In terms of the content, some of it has dated (the limited insight on TV advertising, for instance), but most is as fresh and relevant as ever. Everything from how to motivate people in a high intensity, creative and competitive work environment, to some basic tennets of how advertising works (and how it does not) still makes a very useful, and relatively timeless read.
The shameless self promotion and the colour of the author himself, which come through quite starkly are perhaps a throwback to the 60s, when the book was first written but they are all the more refreshing and entertaining for that. If you are looking for a good quick guide on some basics of running a professional service firm, and do not quite have the stomach for something like
Managing the Professional Service Firm (which I very highly recommend), this is quite a good place to start.