Charles Mann's 1491 is a long and very detailed work, spanning the history of pre-colonial North, Central, and South America back to the earliest discovered civilizations. He covers a lot of ground, so I can only cover the main themes. The societies he focuses on the most include the Inca, the Maya, the mix of cultures that would be called Aztec, the Wampanoag peoples on the coast of Massachusetts, the mound-builder civilization at Cahokia, tribes who built earthworks in the Beni area of the Amazon, and a recently-discovered civilization, one of the earliest known to date, that lived on the coast of Peru.
Mann discusses these cultures in depth, tracing their earliest forms of agriculture, their interactions with neighboring tribes, and the devastation wrought by disease and European conquest. He pays special attention to the cultivation of corn in central America and cotton in Peru. He investigates large earthworks at Cahokia and the Beni, and the cultures that made them. His biggest focus is population. He lays out Henry Dobyn's theory that European estimates of indigenous populations were grossly under-exaggerated, because diseases like smallpox had already wiped out most of the population before the Europeans arrived. Mann also discusses some of the theories about why native Americans were so highly vulnerable to European disease, and the past and present effects of this widespread annihilation.