History

Hard to say if this quite what you're looking for, but the first thing that comes to mind is:

'The Myth of the Good War: America in the Second World War' by Jacques Pauwels

and while we're here he also wrote 'Big Business and Hitler' that I found pretty interesting

Not what I'd describe as an easy or short read, but there is this.

They also call World War 2 by what I think is the best name for the war: "The World Anti-Fascist War".

The Nazi Seizure of Power by William Sheridan Allen is more about the 20s-30s and the lead up to WW2, but I found it very interesting. It focuses on one town and talks a lot about the dynamic between the SDP and NSDAP in a way that I found enlightening. It's a really good on-the-ground look in a field that often zooms out to the point of ignoring the individuals involved.

On the complete opposite side, there's Total War: Causes and Courses of the Second World War by Peter Calvocoressi and Guy Wint. Admittedly, this could definitely fall into your "slog to get through" bucket, but it's not overly academic, just very long (almost 1000 pages I think). It is extremely comprehensive and has one of the best layouts of the lead up to the Sino-Japanese side of WW2 that I've read.

Communist Resistance in Nazi Germany by Allen Merson is pretty much what it says on the tin, it traces the activity of the KPD in a couple of towns over the course of WW2.

All of Kotkin's Stalin books are worth reading (shocking, coming from a Hoover Institute ghoul). The one that would be of most interest to you would probably be Stalin: Waiting for Hitler, 1929-1941. Maybe a bit biographical but an interesting look at the mentality of the USSR leading up to the war.

Hitler's American Friends by Bradley Hart is another one that is pretty self explanatory, goes over stuff like the German-American Bund and Lindbergh's never-was run for president.

Hitler's American Model by James Whitman is best described by its subtitle: "How American race law provided a blueprint for Nazi Germany".

Finally, I know you said no memoirs, but I will always recommend the duo of If This is a Man/The Truce by Primo Levi. It's written by a partisan who was captured and put in Auschwitz and it is one of the most impactful works I have ever read. If This is a Man covers his time in the camp, and The Truce covers his time trying to return to his home in Italy. Definitely would recommend reading them as a pair, If This is a Man is obviously incredibly dark and The Truce is a good palate-cleanser for lack of a better term. (Also The Periodic Table by Levi is a collection of short stories about his time in Fascist Italy and Auschwitz, though it also talks about his time post war and lots of things unrelated to the war.)

You didn't mention what kind of scope you're looking for so I have a few very different recommendations.

First, Night Witches by Bruce Myers is about women Soviet pilots in the Great Patriotic War. It primarily focuses on the so-called "Night Witches", the 588th Night Bomber Regiment/46th "Taman" Guards Night Bomber Aviation Regiment, but there's some good stuff about the other two, the 586th Fighter Aviation Regiment and the 587th Bomber Aviation Regiment. It includes the story of Marina Raskova personally petitioning Stalin to create all-women air regiments, along with oral histories from the women of the 588th themselves. Absolutely incredible book.

Now, forgive me as I commit the sin of recommending a couple books I haven't finished yet because I have a bad habit of not returning to books I've started. For a much, much wider scope on the Great Patriotic War, David M. Glantz's When Titans Clashed: How the Red Army Stopped Hitler is a good book on the topic and covers the whole period of active combat, plus the how both sides' forces were organized and arranged in the lead up.

I know you said no memoirs, but maybe the memoirs of the Marshal of the Soviet Union is a little different? Georgy Zhukov wrote Marshal Zhukov's Greatest Battles in which he details the battles of Moscow, Stalingrad, Kursk, and Berlin. It is also furnished with some maps to give context to what he's talking about at times. It is a memoir, but it's a much wider picture than a memoir from a frontline soldier or something like that. But if that's not what you're looking for, apologies.

This last book is definitely not what you're looking for but I'm going to put it in here for anyone passing by that's interested. I'm going to preface this with an extreme content warning because the contents of this book are beyond harrowing. I cannot emphasize that enough. What the Soviet people experienced during and after Operation Barbarossa is a hell visited upon the Earth that we hopefully will never be able to fully comprehend, because hopefully we will never experience such a thing. The Unwomanly Face of War: An Oral History of Women in World War II by Svetlana Alexievich is an compilation of oral histories from Soviet women veterans. It is incredibly important for that reason, but it is an extremely hard read.

I had to put it down after that and haven't been able to return to it since.

If you're interested in knowing what led to the rise of Mussolini and the fascists in Italy (it is fascinating and so different from what happened in Germany), you have Antonio Scurati's M pentalogy. They're historical novels but they have the level of research and archival sources an academic work would. I've only read M: son of the century, and it was a very well written, well translated read. Very enjoyable, despite its length (each book is around 600 pages long).

Sounds very similar to what you're asking for, despite the first 2 books being about the inter-war period, not WWII per se.