Backstory: A friend of mine was cleaning out some cupboards at the church he works for and came across this. He gave it to me because I like history, but I don't know any German. It's from 1937 and is an army manual of sorts. Can anyone tell me more about it?
That would be the 1937 edition of Die Dienstunterricht im Heere, the Army Service Training Manual. It's got the basic information a recruit would need - camouflage, tactical movement, rifle drill, etc. - and state and military history.
This edition of Der Dienstunterricht im Heere announces itself as the "Ausgabe für den Nachrichtenmann," meaning that it was a version/edition of the book intended for men serving in intelligence. The fourth page that you've photographed lists a few other military textbooks from the same publisher, along with their prices, covering subjects like night fighting ("Das Nachtgefecht"), firearms training ("Die Schießausbildung"), and special topics for NCOs ("Unteroffiziere") and officers ("Offiziere").
The publisher, Verlag E.S. Mittler & Sohn, is very old and actually still exists. As you can see from their offerings, they still publish a lot of content in the military space.
The writer was Dr. Wilhelm Reibert, an erstwhile Captain (later Colonel) in the Wehrmacht. Publication of new editions of Der Dienstunterricht im Heere continued after the war - published and purchased privately, but still regularly updated. Since 1959, the book has actually been called Der Reibert (subtitled Das Handbuch für den deutschen Soldaten). I imagine, though, that new editions no longer give a large portrait of Hitler pride of place on the frontispiece.