Final answer:
Timbuktu's greatest import was books, which were central to its role as a major center of Islamic learning and scholarship under Mansa Musa's rule and thereafter.
Step-by-step explanation:
The question is asking what Timbuktu’s greatest import was during its time as a thriving center of international trade and Islamic education. While commodities like gold and salt were significant in the region, Timbuktu was especially famous for its import of books. The city was a renowned intellectual center during the reign of Mansa Musa and afterwards, wherein many scholars, manuscripts, and books from various regions were brought to the city. This focus on Islamic scholarship and learning, with a flourishing book trade, significantly enriched Timbuktu’s cultural and academic landscape. The trade, collection, and production of books were central to Timbuktu's status, and this contributed to the establishment of libraries and universities, making books Timbuktu's most esteemed import.