Best guide book for South America

Try Footprint or Lonely Planet guides for whatever country you're interested in. I used the Footprint guide for my trip to Argentina and it worked very well, although it was very hard to plan for the region where I traveled (it's not written like a Rick Steves guide, but that's ok). They specialize in Latin America coverage, so that's why I selected their book. I would avoid a book covering the whole continent because it's just too huge - unless you want to compare and contrast different countries before winnowing down your choice.

I used DK Eyewitness and Lonely Planet guides for my trips to Chile, Argentina, and Brazil. They are a bit more heavy than RS guides, but they have numerous insightful graphics that are well work the tad bit of extra heft :)

I like to use my local library to check out various guidebooks for an area so I can see which one(s) suit my travel style and then make a purchase of the latest edition.

BA = Buenos Aires, Argentina? I initially think of British Airways when I see those 2 letters!

In addition to Lonely Planet guides for non-European destinations, there’s also Rough Guide, a British series. Some of their maps are the best, both for out-of-the-way destinations and cities with lots of sights.

Aside from Rick’s books, though, Lonely Planet has usually been our next choice. They don’t come out with updated versions as frequently as Rick, however. Not having been to South America yet, can’t give you a direct recommendation, but from experience with other continents, Lonely Planet and/or Rough Guide are well-written, well-researched, and provide good recommendations. Each tends to be aimed at a slightly more backpacker-type, lower-budget traveler than Rick’s guides. Buen viaje!

DK Eyewitness are my favorite travel books.
You will love Machu Picchu and Cusco. Get ready for some climbing. We did it last year. I was 71 then and an active person. Still, all the climbing in Cusco, the Sacred Valley and Machu Picchu (with the altitude) wore us out after four days.

Be sure to have you physician prescribe you pills for the altitude. Cusco is over 11,000 feet, some ancient ruins are 12,000 feet above sea level.

We used Peru Agency for our tour. It was inexpensive ($799 per person for four day tour) and excellent.
Lima is worth 2-3 days.
Love South America, it is cheaper than Europe and lots to see. Also, love Argentina and Chile.