Excerpts from Books and Wikipedia
"Even before he had become king of England, John's frequent conspiracies against his brothers, Henry, Richard, and Geoffrey, gave him a reputation for treachery. His reign has generally been labeled as one of the most disastrous in English history. . . . However, he is chiefly remembered for bringing misfortune on his kingdom through his dispute with the pope and his wars with France, taxing his barons to the point of civil war, and being forced to submit to the laws of Magna Carta at Runnymede on June 15, 1215." [1001 Days]
"No taxation without consent, limitation of the king’s power to seize and punish: it was, as the contemporary Chronicle of Melrose remarks, “a new state of things . . . in England; such a strange affair as had never been heard.” The Chronicle is incredulous: “The body wished to rule the head, and the people desired to be masters over the king,” it marvels. But John had pushed his barons too far, and the defeat at Bouvines had weakened him just enough for them to push back." [Bauer: Renaissance World, p. 252]