The Secret History of the Mongols (anonymous, 13th century, translated by Igor de Rachewiltz or Francis Cleaves) is the essential primary text — the oldest surviving literary work in the Mongolian language, recording the rise of Genghis Khan and the early Mongol empire. Reading it before or during a visit to Inner Mongolia changes how you see the landscape. It is a chronicle of extraordinary ambition and equally extraordinary violence, written with a directness that no modern historical account quite matches.
Genghis Khan and the Making of the Modern World by Jack Weatherford is the accessible modern account of the Mongol empire's global impact. Weatherford is particularly good on how the Pax Mongolica enabled the movement of goods, ideas, and diseases that shaped the modern world. His subsequent book, The Secret History of the Mongol Queens, focuses on the women of the empire and is equally readable.
Wolf Totem (狼图腾) by Jiang Rong is a Chinese novel set in Inner Mongolia during the Cultural Revolution, when the author was sent to the steppe as part of the educated youth campaign. The novel is a meditation on the relationship between nomadic and agricultural Chinese culture, told through the story of a wolf cub raised by a Han student. It was a massive bestseller in China and remains the most widely read literary treatment of Inner Mongolian life. Some of the ecological and historical arguments have been contested, but as a way into the landscape and its contradictions it is unsurpassed.