Alternatively anything about the Greek period through to the enlightenment. In French or English, and even just a general history of medieval southern France would do.
/u/WelfOnTheShelf and I list some books on the Albigensian Crusade before in: (SASQ) I'm prepping a tabletop RPG campaign set during the Albigensian Crusade (yes, my life is that cool) and I'm trying to better understand the period and the region.........
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In French (that I'm not really good at), I'd recommend the works by Laurent Macé, Florian Mazel, and further, possibly Jean-Louis Biget & Jean Duvernoy (the last as a editor of some indispensable sources like the inquisition records), in addition to the famous classic, Montaillou, village occitan de 1294 à 1324 (1975: French orig. / 1978: English trans.) by Emmanuel Le Roy Ladurie.
As a French reader you should avail yourself of theHistoire générale de Languedoc. It's an incredible primary source that many French and Occitan historians are still using. It covers centuries of Medieval Occitan history. I'd also highly recommend you read all of Michel Roquebert's L'Épopée cathare books. He is still a frequently referenced secondary source and is considered the most definitive work on the Albigensian Crusade.
Linda Paterson's The World of the Troubadours: Medieval Occitan society c. 1100 - 1300 is still the most comprehensive work on Occitan society. It covers virtually everything you can think of. Paterson's work is definitely relevant, though our understanding of the war, heresy, have evolved.
Heresy, Inquisition and Life Cycle in Medieval Languedoc by Chris Sparks is a fantastic follow-up that continues on in the vein of Paterson, though it's more recent at the expense of being less comprehensive. It's also much narrower in chronology than Paterson.
Ermengard of Narbonne and the World of the Troubadours by Fredric Cheyette is a fantastic case study of an Occitan noblewoman preceding the Albigensian Crusade. It intersects with so many aspects of life in Medieval Occitania while highlighting the uniqueness of Occitan culture.
Elaine Leigh-Graham's The Southern French Nobility and the Albigensian Crusade is a wonderful follow-up to Cheyette's work. If you want to follow the drama of Occitan politics, social conventions, and how the Crusade influenced these, then read this.
Kill Them All: Cathars and Carnage in the Albigensian War by Sean McGlynn is a great overview of the Albigensian Crusade and the military campaigns against Cathars. The book is somewhat popular history, but I would recommend it over works like A Most Holy War which is extremely sensationalist. Pegg's assertions that there were never any Cathars and that the crusade was a series of mini-holocausts is outlandish. McGlynn focuses more on the military operations at the expense of leaving the religious items on the side. For a more in depth history, specifically the first half of the crusade, I'd highly recommend The Occitan War by Laurence Marvin.
That's all I can think of, for now. If there are any specific topics you'd like more information do let me know.