The first two verses refer to the miracle of the splitting of the moon by the Prophet when the Makkans demanded a miracle. Bearing witness to both the halves on either side of Mt Hira they dismissed it as magic.
After warning of the day of judgement the sura cites the people of Prophet Nuh, the tribes of Aad & Thamud, the people of Prophet Lut and the people of Pharaoh who were punished for rejecting their messengers. It concludes with the inevitability of accountability and the promise of Janna and a permanent place of honour for the God conscious.
An emphasis on the ease of internalising the message of the Qur’an with a minimal amount of effort is repeated four times.