Herodotus’s Histories is a major source for the Greco-Persian Wars and the wider world that led to them. It covers Persian, Lydian, Egyptian, Scythian and Greek settings before moving into the Ionian Revolt, Marathon, Thermopylae, Salamis and Plataea. The work is valuable for readers wanting narrative detail about places, customs, rulers, battle traditions and the way Greeks later explained the Persian invasions.
Herodotus does more than narrate campaigns. He collects speeches, origin stories, geographical descriptions and reports of customs, often preserving several explanations before stating which he finds most convincing. That mixture makes the work indispensable but also requires critical reading, since observation, oral tradition and storytelling sit beside one another throughout the text.
Plutarch
Xenophon
Arrian
Thucydides
Diodorus Siculus