'The desert city of Chinguetti, sinking ever-deeper under the sands of the Sahara, is the last place in the world you would expect to find a library. Yet this crumbling outpost in the west-African country of Mauritania is home to around 6,000 rare books and manuscripts, including some of the oldest Koranic texts in existence which date back to the 9th Century. It was once the prosperous and bustling trade centre of several 'trans-Sahara' trade routes. Traders from all over Europe, north-Africa and the Levant would stop in Chinguetti before moving on to sub-Saharan Africa. There, they would rub shoulders...