The book is a photographic memoir by Brassai featuring a series of daring and previously unpublished 'secret photographs'. It captures the hidden side of Paris, where high society intertwined with the underworld, revealing the city's forbidden and sordid aspects. The collection explores themes of clandestine encounters and the juxtaposition of different social strata within Paris. The memoir provides a unique glimpse into this unseen world, showcasing Brassai's ability to convey the city's complex social dynamics through his lens.