Exploring Cusco is the classic guide to the Cusco region and Machu Picchu. It combines city and country walking routes with Inca history, maps, illustrations, local lore, and fascinating sidelights on the Inca heartland. First published in 1979, the book has been through five editions and is currently out of print pending publication of the sixth edition in 2018.
Machu Picchu Historical Sanctuary is a color photo book intended as an informative and eye-catching souvenir of the famous Inca site. With text and some photographs by Peter Frost, along with photos by many other talented contributors, the first edition was in print for many years.
The Pocket Guide to Ecuador, 2005. With all text and photographs by Peter Frost, and a special section on the Galapagos, another brisk pocket guide in the Insight Guides series of suggested itineraries.