The year 1492 is best known for Columbus' discovery of America (though he thought he had got to China); also for the conquest of Granada by the "Catholic Monarchs", which put an end to the Moorish civilisation in Spain (which had been rather tolerant), replacing it with a very intolerant one (NB the Inquisition and the eviction of the Jews). Even if you think you already know about these events, Fernandez-Armesto is well worth reading.
His discussion of the earlier Spanish colonisation of the Canary Islands, though it comes in a separate chapter, provides an interesting preamble to the subsequent overthrow of the Inca and Aztec civilisations.
At least equally important, and much less well-known, were events in the Far East and around the Indian Ocean, which the book discusses at some length. Around this time, China withdrew from imperial ambitions, while Japan "crumbled into ineffectiveness", leaving that very important area open to subsequent European trading and colonisation.
There is also a chapter about events in Africa in and around 1492, which shaped the religious map of the continent, Islam dominating across the Sahara, in the Sahel and along the Indian Ocean coast, with Christianity preponderant elsewhere.
The author's breadth of knowledge is impressive - he has a Spanish father, an English mother and lives in the USA, which may contribute to this. Though I found myself skipping some parts - such as the dynastic vagaries of Imperial China - I found his book both readable and instructive.