A rummage among dusty charity-shop bookshelves unearths a gem of a recipe for spicy-sour courgette suffused with the fresh taste of mint For the past 10 years, some of my best cookbook purchases have been from Oxfam on London's Marylebone High Street and the Mercatino dell'Usato in Monteverde in Rome. I visit both as often as possible, always feeling the same high on book-buying endorphins as I make a beeline for the cookery shelves.