Mahabharatha is the longest epic in the world. In the present form, it contains 1 lakh verses. It was originally called Jaya, meaning victory. By common consent its author is recognised as Vedavyasa.
Mahabharata is centered around an epic war between cousins in a royal family for the throne. The story, told briefly, is given below: (A complete book about Mahabharata on wikibooks is planned for near future).
The story happens in the kingdom of Hastinapura. The eldest son of the late king, Dhrutarashtra, is born blind, so his younger brother, Paandu, takes up the throne. But due to a curse by a scholar, or Rushi, he dies in a forest along with his second wife, Maadri. The throne is held by Dhrutarashtra. Paandu's first wife, Kunti, brings their five children, Pandavas, back to the city, where they are taken care of by their great-grandfather Bhishma. Pandava brothers are: Yudhishtira, Bhima, Arjuna, Nakula, Sahadeva. Dhrutarashtra has one hundred sons, eldest of whom is Duryodhana. Dushasana is his second son. Duryodhana, is ambitious of becoming king himself. But he learns that as long as the Pandava brothers survive, he can not be made a king according to the laws. He and the strongest of the pandava brothers, Bhima, become mortal enemies.
Duryodhana forms a close friendship with a great archer, Karna. Karna is the equal of Arjuna, the younger brother of Bhima, in archery. Together with Karna, Duryodhana plans to win pandavas in war. Duryodhana's maternal uncle, Shakuni, poisons his mind and encourages him to employ devious tactics. As a result of these teachings, Duryodhana tries to kill the pandavas and kunti by setting fire to a wax house he had made for the pandavas. But the pandavas escape and live in exile for an year. At the end of the year, they come back, now having married Draupadi. All five brothers are married to the same woman.
Shakuni continues to poison Duryodhana's mind, and this culminates in a cheating game of dice where Yudhishtira loses everything he owns, including his kingdom, to Duryodhana. Yudhishtira plays his own brothers, himself, and his wife in the hope of winning everything back, but loses. Draupadi is humiliated and Dushasana tries to disrobe her in public, but lord Krishna intervenes and saves Draupadi. Bhima vows to kill both Duryodhana and Dushasana, while Arjuna vows to kill Karna, who had humiliated Draupadi during the dice game. As a result of their loss in the dice game, the pandavas are exiled from their kingdom for a total 13 years: 12 years of forest living and 1 year of hidden living.
At the end of 13 years, Duryodhana refuses to give back the kingdom, and takes the stance that his final aim in life is to kill the pandavas, Bhima in perticular, no matter how much harm the war might bring. This leads to the great war.
In the great war, lord Krishna becomes the charioteer of Arjuna, and helps the pandavas to win. All the great warriors of Duryodhana's side are killed one after the other, and Bhishma, who fights alongside Duryodhana, falls awaits his death amidst the raging war. On the day before the final day, Bhima kills Dushasana, and Arjuna, in what is perhaps the most famous war-story told in the history of Sanksrit literature, kills Karna. But after the war Arjuna discovers that Karna was his eldest brother, born to Kunti before marriage. Krishna reveals that he had known this all along, and had arranged Kunti to talk to Karna before the war so that Karna won't kill any of the pandavas. He himself talks Karna into not killing any of his younger brothers except Arjuna, whom Karna vows to kill, or be dead himself.
On the final day of the battle, an epic battle ensues between Bhima and Duryodhana, and finally Duryodhana falls.
The story contnues to talk about pandavas rule after the war, and ends with all the eldest of the pandavas, Yudhisthira, entering the heaven alive.