Over Time is a short book about a long one. For twenty-four years and counting, Alessandra Sanguinetti has photographed two cousins, Guille and Belinda, as they grew up in the countryside of Buenos Aires Province — a series in which the subjects have been collaborators and playmates rather than sitters. This reader does not restage that work. It sets it talking.

The core of the book is an extended conversation between Sanguinetti, Guille and Belinda, in which they look back at how the photographs were made and at what their relationship to them has become. A second exchange, with the curators Clément Chéroux and Pierre Leyrat, takes up the harder questions the series raises: what documentary photography can claim, what artistic collaboration means when it lasts decades, and how the lives of girls and women are pictured.

Threaded through the discussion are images from across the years that have not been published before. The book itself is modest in scale — sixty pages, paperback with a flap, bilingual in English and French — and belongs to MACK’s DISCOURSE series, in which an artist, theorist or writer holds a single subject in view for the length of a text. It appears alongside a solo exhibition of Sanguinetti’s work at the Fondation Henri Cartier-Bresson in Paris, opening 30 January 2024.

For collectors, the interest here is circumstantial rather than spectacular. Over Time is not a picture book to set beside the Guille and Belinda volumes; it is the argument that surrounds them, conducted by the people who made the work and by curators who have thought about it at length. The previously unseen frames make it a natural companion to those books, and the bilingual edition carries the conversation into two readerships at once. Read after the photographs, it alters what they appear to be doing.