philipl, a bit of an open question there in my opinion...
If your question refers to books ABOUT Peru (history, politics, people, culture, etc) then I am clueless as to books on that subject.
However, if you are planning to travel to Peru then the Rough Guide book is fine. It also BRIEFS you on the history, politics, people and culture of Peru. Note however that the 'Rough' in 'Rough Guide' should be taken literally at times of travel.
In addition, before I went I did a lot of research on the 'net and I found web travelogs to be probably the most useful sources of information before journeying to Peru.