I've been trying to read more into the inner workings of the Nazi regime, especially from the perspective of those who were either within it themselves or had access to people who were.
I've come across "The Goebbels Diaries", are these of historical note and do they have much insightful information in them? If not, could you please point me to some other resources that are informative, especially on Joseph Goebbels himself.
Are the "Goebbels Diaries" insightful into the inner workings of the Nazi regime?
Yes and no.
Goebbels's diary was not a diary in the conventional sense of the word. The diary was not a personal reminiscence of a day's events in the style of Anne Frank. Instead, Goebbels saw his diary as a personal testimony to his own importance within Germany. During the 1920s, the diaries cast its author as something of a romantic figure acting in tumultuous times. The Nazi seizure of power caused a shift in which Goebbels used the diaries to place himself at the center of a political movement he saw as globally transformative. By the invasion of the USSR, Goebbels dictated his diary entries to stenographers and they often included materials related to his governmental duties. This underscores the semi-public nature of the diaries and Goebbels very likely anticipated they would be used to either celebrate his triumph after Nazi victory, or vindicate him in the case of defeat.
Goebbels's most recent biographer Peter Longerich notes that the diaries are reasonably accurate in terms of recalling conversations and the basic contours of Goebbels's role within the government. Longerich also contends while being "in essence generally correct,":
But time and again the diaries also feature freely invented strategic assertions from the workshop of Goebbels the propagandist, assertions that he clearly intended to reproduce in his later publications. Such distortions and inventions are particularly valuable for a biography. They provide us with the key to understanding Goebbels’s perception and interpretation of certain situations. But to come to terms with them properly, the diaries must, if possible, be weighed against other historical sources.
As the above excerpt from Longerich shows, the diaries are a pretty dicey historical source taken alone. While his entries gingerly dance around the murder of Jews, a knowledge of Holocaust scholarship fills in the gaps his diaries deliberately leave out and explain the euphemisms typical within the Nazi vocabulary like evacuation being a synonym for liquidation (i.e. murder). Goebbels was keen to present both the justness of his cause and his importance within it. Not surprisingly, Goebbels comes across as a vain, banal, and self-aggrandizing blowhard in the diaries. There is also next to no self-analysis. German failures are the result of others' incompetence, never Goebbels or his master, Hitler.
My suggestion to learn from the Diaries is to read Longerich's biography instead of the diaries. Longerich drew extensively from them so much that the Goebbels estate sued Random House for a slice of royalties.