Perhaps Proust bought some of his books here. I certainly did in more recent times. Another great place was the early Saturday morning book market at the Parc Georges Brassens near the Vanves Metro station. I remember sitting at a great Moroccan bistro on the side of Park over a good couscous with a glass of Beaujolais, after I bought some books of course.
Perhaps the bistro is still there who knows. Dealers? Yes, even the Parisian Hi-brows bought there and more than one photo book dealer got his start there selling those picture books cheap before migrating to New York or a classy uptown Paris address. No, no names please.