Thomas Gloning & Christopher Young 
A History of the German Language Through Texts [PDF ebook] 

A History of the German Language Through Texts examines the evolution of German, from the Early Medieval period to the present day.
Written in a lively and accessible style, the book looks at the history of German through a wide range of texts, from medical, legal and scientific writing to literature, everyday newspapers and adverts. All texts are translated and accompanied by commentaries. The book also offers a glossary of technical terms and abbreviations, a summary of the main changes in each historical period, a guide to reference material, and suggestions for further reading.
A History of the German Language Through Texts is essential reading for students of German, Linguistics or Philology.