The historiography of 18th century France has a notable split, many historians and books right up to the Thermidorian Reaction, but the Directory is a kind of no man's land before the rise of Napoleon brings a different kind of historian to the fore. Military history is written and read by different people from academic history-- the Directory marks a divide between these two different sorts of practitioner and audience and Barras as a subject falls between them, neither fish nor fowl.

He’s a key figure in the rise of Napoleon - gives him his first command, not to mention Josephine, and while Barras imagines that he has a deal with Talleyrand and the Bonapartes (Napoleon & Lucien) in the Coup Brumaire, they have little use for him they day after- he is encouraged to enjoy a comfortable retirement, which with some bitterness he accepts and departs the stage.

None of the figures of the Directory get much attention from Anglophone historians -- not the mathematician/logistician Lazare Carnot whose policies of "careers open to talent" is at least partly responsible for the remarkable cohort of young aggressive military leadership that emerges in the 1790s, nor Joseph Fouché -- Fouché has a career stretching from revolutionary zeal to Napoleon's policeman, to the Bourbons. Only Talleyrand excites some interest, and that's more on the colorful anecdote side of the fence. In English one of the few academic historians working on this period is Isser Woloch at Columbia (Napoleon and his Collaborators [2001])

Why this falloff in interest by academic historians?

The period up to the Revolution is a perfect fit for modern ideas in the practice of history. Lots of data -- the French kept wonderful records, much of which survive-- grist for the mill. One can easily identify half a dozen eminent Marxist historians of the Revolution, and another half a dozen revisionists responding to those Marxists. There are few such battles over Napoleon; just shelves groaning with the weight of military histories written for popular audiences.

When you get to the Thermidorean Reaction, the Directory and its demise in the Coup Brumaire, we’ve got an abundance of colorful characters like Barras, Fouché, Talleyrand, Napoleon -- and minor figures like Rewbell. . . we're into a history of personalities, not data. Whether they're "great" men or just ordinary men - or indeed great women such as Germaine de Stael-- this kind of history of personalities is not where the practice of academic history is today. Its "story telling"; indeed Barras tells us his own story, entertainingly, in his memoirs which are even occasionally reliable. One of the amusing things about the period is that everyone writes their memoirs, and there are also plenty of fraudulent memoirs (for example of Talleyrand and Fouché); unsurprisingly they tend to cast themselves in a favorable light.

So we just don't get a lot of the in depth historical study of these characters that we might expect-- even in French it's surprisingly thin on the ground. There is no equivalent to "Twelve Who Ruled" -- R.R. Palmer's classic account of the Committee of Public Safety -- for the Directory.

But we do have memoirs, endless memoirs. You can read about Barras in his own memoirs, read it against those of Talleyrand, those of La Révellière-Lépeaux, those of Napoleon and more. The impression that's left is of an opportunist, quite full of himself, but without any particular vision, someone overwhelmed by the sea of talent around him. He was a practical man, and more eager to enrich and enjoy himself than devoted to any particular political vision; that is, a practical politician in an age of more dramatic ideologues. And, unfortunately, a letter of 1910 informs us that Barras' personal papers were destroyed accidentally some years earlier; other than Barras himself no one seems to have made use of them.

You will find a few biographies of him in French, for example "Barras, roi du Directoire" [1970]; in addition you'll find portraits in more general histories in English of Thermidor and the Directory generally -- these have quite a bit on Barras. But Napoleon looms so large that he sucks the air out of the room-- all sorts of figures who were more familiar as names at the time get little historical attention today; Hoche and Pichegru are footnotes, the Duc d'Enghien prompts a google search every time someone starts War and Peace, the Abbé de Pradt is another of those names you have to check. Of the secondary figures of the period, Babeuf and Barère are likely the ones that have attracted the most attention from historians -- they have a particular importance for Marxists and historians of terror.