on March 26, 2011
It's a typical Lonely Planet... you get all the info you need and more. Unfortunately the inflation is really high in Argentina... I believe 22% last year so even if you have the latest issue the prices in the book are not accurate anymore. Park entrance fees for Iguazu went up from 60 to 100 Pesos in January 2011 for example.
I always buy an additional travel guide with a few pictures so I have a better idea but for general info it's a very complete book.
I also found the section on Uruguay very useful since a lot of travelers include that smaller country in their Argentina trip.