You can find the Maupetit bookshop on La Canebière, one of the main boulevards in Marseille. They have a really good selection of books (including English language) and hold a lot of reading events. This is at the more professional end of book shops (rather than a place where you can rummage through piles of dusty books) and a great place to find a specific book that you’re trying to track down.
Opening hours: Monday to Saturday, 10am to 7pm. Closed Sundays.