Simplicissimus by Johann Grimmelshausen

Simplicissimus by Johann Grimmelshausen. The Catholic Encyclopedia calls him "The greatest German novelist of the seventeenth century." Sounds impressive, but how many German novelists were there in the 17th century? There are lots of historical novels written about 17th century Europe, but not so many written then as you see on this excellent website.

The original 1669 book cover.

According to Wikipedia, Simplicissimus is a picaresque novel published in 1669 and written in the Baroque style. The tale was inspired by the events and horrors of the Thirty Years' War which had devastated Germany from 1618 to 1648, it is regarded as the first adventure novel in the German language.
 
The classic history of the the Thirty Years' War was authored by C.V. Wedgwood. Sample it on Google Books.