This is a text that combines two schools of studying programming languages: by survey and by writing interpreters. The book uses Scheme for the interpreters, but surveys several other languages along the way.
The book does not itself teach Scheme, so a background in Scheme from one of the standard category-texts would be helpful. The book has minimal other prerequisites.
The book is available from http://www.cs.brown.edu/~sk/Publications/Books/ProgLangs/
The author, Shriram Krishnamurthi, is also a co-author of PLT-Scheme and of HtDP.