Xerxes was not the first-born son of Darius, but he was the first son of Darius' wife Atossa, the daughter of Cyrus (HDT.7.2), which put him in the succession.
Xerxes suppressed a revolt in Egypt. He fought against the Greeks in the Persian Wars, winning a victory at Thermopylae and suffering defeat at Salamis.
Herodotus states that when a storm damaged the bridge Xerxes had had built across the Hellespont, Xerxes got mad, and ordered the water be lashed and otherwise punished. In antiquity, bodies of water were conceived of as gods (see Iliad XXI), so while Xerxes may have been deluded in thinking himself strong enough to scathe the water, it is not as insane as it sounds: The Roman Emperor Caligula who, unlike Xerxes, is generally considered to have been mad, ordered Roman troops to gather seashells as spoils of the sea. After the scathing, Xerxes made his bridge across the Hellespont by lining up ships next to each other. (Incidentally, Caligula did the same thing to cross the Bay of Naples on horseback in A.D. 39.)
Herodotus (HDT) Books 7, 8, and 9 are the main ancient sources on Xerxes.
