Adolph Freiherr Knigge (16 Oct 1752, Bredenbeck bei Hannover - 6 May 1796, Bremen) was a German author and a noble. He was also a member of the Illuminati.
From 1769 to 1772, he studied law in Göttingen. He went on to hold several high positions in the court of Weimar, including chamberlain in 1777. He joined the Illuminati in 1780, and his work for them led to great publicity. Due to conflicts with the group's "stiff-necked" leader, he left in 1784.
A good deal of Knigge's work involved the advancement of human rights. This and his history with the Illuminati eventually caused a loss of respect for the fellow among his aristocratic peers, and, combined with a period of illness, eventually to the loss of his wealth.
The broken Adolph travelled to Bremen, where in 1790 he obtained a scholarly position and regained financial stability for the last six years of his life.
In Germany, the man is best known for his 1788 work Über den Umgang mit Menschen (On Human Relations). What he is not known for, however, is the actual, original intention of this work. Written as a sociological treatise on the peculiar and very particular way wealthy humans decide to interact with each other, Über den Umgang mit Menschen was universally misinterpreted (and very well received) as a sort of manual or how-to guide for high-class etiquette and manners - right down to which side one ought to stand when removing a lady's coat.
Nowadays, the word Knigge is synonymous with prim-and-proper etiquette in Germany - people are scarcely aware of the original work. Going to a restaurant for an important job interview? "Better brush up on your Knigge," people will suggest. If, as I did, you look for anything by Knigge in a book shop, you won't likely find the original work, but rather condensed guides with names like "Pocket Knigge" and "Knigge for Restaurant," often updated to keep with modern times. You'd have to have it special-ordered, or just follow the Project Gutenberg-DE URL at the bottom.
The following list of his works is taken directly from the Project Gutenberg-DE page. None of his works have been translated to English, that I can find, but I am currently working on translating Über den Umgang mit Menschen as a fun (fun?) project.
1778 Allgemeines Sistem für das Volk zur Grundlage aller Erkenntnisse für Menschen aus allen Nationen, Ständen und Religionen
1781 Der Roman meines Lebens
1783 Sechs Predigten gegen Despotismus, Dummheit, Aberglauben, Ungerechtigkeit, Untreue und Müßiggang
1783-85 Geschichte Peter Clausens
1784 Gesammelte politische und prosaische kleinere Schriften
1786-90 Bekenntnisse (Übersetzung des Rousseauschen Werks aus dem Französischen)
1787 Die Verirrungen des Philosophen oder Geschichte Ludwigs von Seelbergs
1788 Philo's endliche Antwort auf verschiedene Anforderungen und Fragen, meine Verbindung mit dem Orden der Illuminaten betreffend
1788 Über den Umgang mit Menschen
1789 Geschichte des armen Herrn von Mildenberg
1790 Benjamin Noldmanns Geschichte der Aufklärung in Abyssinien (Novel)
1790 Über den Zustand des geselligen Lebens in den vereinigten Niederlanden
1791 Das Zauberschloß oder Geschichte des Grafen Tunger (Novel)
1792 Politisches Glaubensbekenntnis von Joseph Wurmbrand (Essay)
1792 Die Reise nach Braunschweig (Novel)
1792 Erläuterungen über die Rechte des Menschen. Für die Deutschen
1793 Über Schriftsteller und Schriftstellerey (Essay)
1794 Geschichte des Amtsraths Guthmann
1795 Reise nach Fritzlar im Sommer 1794 (Satire)
*Project Gutenberg-DE (http://gutenberg.spiegel.de/?id=19&autor=Knigge,%20%20Adolph%20Freiherr%20von&autor_vorname=%20Adolph%20Freiherr%20von&autor_nachname=Knigge)
*A very interesting conversation with the very knowledgeable proprietress of a book shop in Telgte, DE