Help my Grandmother

I recieved an interesting letter from my grandmother and was hoping the wallstreetoasis community could offer some recommendations.

"I would like to understand 'the value of currencies' (E.g., the value of the U.S. dollar, how values change, in relation to international currencies, who makes what decisions and how, some history of changes and international agreements since the 1940s). Can you recommend a text(s) that is relatively simple, clear?

Hope the prospective internships are interesting.

Love,
Sheen"

A little background on my grandmother:
88 years old, 100 pounds
Smokes half pack a day and has about 6 full glasses of wine a day (but holds it better than me)
Undergrad at University of Chicago, masters at Columbia
Divorced my grandfather 35 years ago
Very strong willed (cannot emphasize this enough)

Please keep in mind that she is fairly intelligent and is going to do whatever she wants. I am just a finance major and do not know too much on the subject, but if anyone out there has any suggestions I would really appreciate them.