I used this book loads while traveling around South America, and as always it has been the backpackers bible. That in itself can be a problem, however, as it does make the planet not so lonely as there are always other people going where you are going.
While I love the LP format, layout and info provided, sometimes it does leave things out that are worth doing/visiting, or give them a bad subjective review. I've also found maps to be incorrect.
As with all research, it is better to have more than one source, but as with all travelers, I also wanted to travel light. All the same, I found using South American Handbook 2011 (Footprint Handbook): 87 (Footprint South American Handbook)
along side this invaluable (not this edition though, and bare in mind older books are cheaper and the sites barely change). The format isn't as easy-reading, but the objectivity allows more facts to be squashed in, giving extra places to visit that are worth seeing, while including extra logistical info such as accom and travel details.
Tip: In an age of digital cameras, instead of dragging 2 guides books out and about with me daily, I took photos of the relevant pages which having sometimes already read, I could easily refer to and read on my camera. This meant I could go out with sometimes 1 and sometimes no guidebook - who needs an extra 3kg of book in their daypack, yet you'll always have your camera?!
Follow your dreams and enjoy your adventure - I did!