Not the play by Bertolt Brecht, but the 17th century book that inspired Brecht’s play.
About the author (from Wikipedia):
Grimmelshausen’s work is greatly influenced by previous utopian and travel literature, and the Simplicissimus series attained a readership larger than any other seventeenth-century novel. Formerly, he was credited with Der fliegende Wandersmann nach dem Mond, a translation from Jean Baudoin’s L’Homme dans la Lune, itself a translation of Francis Godwin’s The Man in the Moone, but recent scholars have denied this; he did, however, write an appendix to a 1667 edition of that translation, the basis for that association. Der fliegende Wandersman was included in his collected works, though without the appendix.
In 1668, Grimmelshausen published Der abenteuerliche Simplicissimus Teutsch, d.h. die Beschreibung des Lebens eines seltsamen Vaganten, genannt Melchior Sternfels von Fuchsheim, which has been called the greatest German novel of the 17th century. For this work he took as his model the picaresque romances of Spain, already to some extent known in Germany. Simplicissimus has been interpreted as its author’s autobiography; he begins with the childhood of his hero, and describes the latter’s adventures amid the stirring scenes of the Thirty Years’ War. The rustic detail with which these pictures are presented makes the book a valuable document of its time. For some, however, the later parts of the book overindulge in allegory, and finally become a Robinson Crusoe story.
The historian Robert Ergang draws upon Gustav Könnecke’s Quellen und Forschungen zur Lebensgeschichte Grimmelshausens to assert that “the events related in the novel Simplicissimus could hardly have been autobiographical since [Grimmelshausen] lived a peaceful existence in quiet towns and villages on the fringe of the Black Forest and that the material he incorporated in his work was not taken from actual experience, but was either borrowed from the past, collected from hearsay, or created by a vivid imagination.”