We have some mods specializing in Italian fascism and Nazi Germany, but I would suggest the following:
Begin with Paxton’s “The Anatomy of Fascism”, and then pick up Eatwell’s “Fascism: A History”. You’ll want to get into Nazi Germany eventually, and for that Richard Evans has written an excellent trilogy on it, and Thomas Childers has written a fantastic one-volume history, both of which I’d strongly recommend reading before you go any deeper on the nazis
You will eventually want to pick up Kershaw’s “The Nazi Dictatorship: Problems and Perspectives of Interpretation, 4th edition” as it explores some of the key debates in Nazi German history, including an essay on fascism. After that I’d recommend Payne’s “History of Fascism”. If you need some background reading, the last three books of the penguin history of Europe are what you want. These are also written by Evans and Kershaw
My own speciality is the debate around whether or not imperial Japan should be considered fascist or not
For that (and I would strongly suggest you read these only after reading two or three of the books I’ve already mentioned so you have the background of fascism) I would recommend, in reading order:
The Rise of Modern Japan, Beasley Modern Japan: A Historical Survey, Hane Grassroots Fascism, Yoshimi Japan’s Total Empire, Young Modern Japan, McClain Hirohito and the Making of Modern Japan, Bix The Culture of Japanese Fascism, Tansman The Aesthetics of Japanese Fascism, Tansman Fascism and the History of Prewar Japan, Duus The Taming of the Samurai, Ikegami Military Intervention in Prewar Japanese Politics, Gow The Dark Valley, Brendon Japan in the Fascist Era, Reynolds Rethinking Emperor-Centered Fascism, Bix The Search fora New Order, Fletcher
There is of course much more to say, but hopefully you find this a useful start!
*I apologize about formatting. Can’t seem to get the titles to form into a column
/u/Klesk_vs_Xaero and /u/Orel_Beilinson have previously answered What are some works on the history of Italian fascism?
Have a look at the Spanish Civil War section of the subreddit booklist curated by /u/crrpit as well.
Click here for links to a series of answers on the subreddit about the nature of fascism.